Upgrading from 128esr to the latest Release version should be straight forward. See https://support.mozilla.org/en-US/kb/thunderbird-release

Backing up the existing profile prior to upgrading is crucial. But there is no need to export and import the profile, you just keep using your existing one.

Please explain what you were doing in more detail, and why you were messing with the profile.

After several hours of this, I finally decided to download version 139 using the standard Mozilla set up even though my Thunderbird 128 version is located someplace else.

What does this mean? Didn't you use the 128esr version from https://www.thunderbird.net/ ?

Yes, the version of Thunderbird I am using is 128esr that I downloaded from www.thunderbird.net. Also, I followed the instruction for the release of 139. I think my issue is that I downloaded the new version of Thunderbird using the standard download without realizing that my old version of thunderbird is in a different location on my c drive. I don't know how the old version is not in the standard location. I would not have done a custom download for the previous install.

So, now I have two versions of thunderbird on my computer. They both work. My old one with all my profile data and a new one with no data. Rather than risk loosing my profile data, I was hoping to create a copy of my profile and somehow put it someplace where the new version of Thunderbird could recognize and use it. That is why I am fooling with the Profile.

I expect you would recommend I find where the old App of Thunderbird resides; uninstall the new version I just downloaded and re-install the new version it in the same location as my old 128esr version. I know how to do all that. But not only is my Thunderbird App in an unexpected location on my C drive, it appears that my Profile is also in an unexpected location. I can't be certain that my custom download will figure that out. I don't trust myself to do a custom download without loosing my Profile data. I am just not that tech savvy. I am not even sure my zip backup works. I say that because when I go to Help\Troubleshooting Information and select "aboutprofiles" Thunderbird shows a "yes" next to the default Profile showing that my old version is using the defualt-esr profile. But when I select Open Folder for the Default profile I get an error message that says Thunderbird cannot find the file.

I want to upgrade. But I don't trust myself to do a custom download without loosing my Profile data. Maybe I am just not tech savvy enough to upgrade Thunderbird.

I expect you would recommend I find where the old App of Thunderbird resides; uninstall the new version I just downloaded and re-install the new version it in the same location as my old 128esr version.

No, it actually doesn't matter where the 128esr version is installed. And there is no point re-installing the new version.

Start the new version, check which profiles exist, and which one is actually being used by the new version. At the top right of the Thunderbird window, click the menu button ≡, then select Help > Troubleshooting Information. Under the Application Basics section, find the 'Profiles' row, then click on about:profiles.

Please post a screenshot showing the existing profiles on the about:profiles page. https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

I appreciate all the time you are giving me Christ1

christ1 is offering good advice.

I'd be very interested to know precisely where on c:\ that esr128 was installed. I know of cases where it is not where we would expect - in a temp directory for example.

So you're now running TB139 with the profile 'Default User', but it has none of your data, correct?

Try the other two existing profiles 'default-release' and 'default' by clicking the corresponding 'Launch profile' button. If one of those profiles shows all your data, set it as the default profile, by clicking the 'Set as default profile' button.

When Thunderbird 139 starts with the correct profile again, you can uninstall the TB128 application.

I launched the other two profiles. Each time it opened a new Thunderbird but non of them have my Profile data.

I'll be more detailed in my response: So you're now running TB139 with the profile 'Default User', but it has none of your data, correct? - That is correct. I successfully launched the other two profiles. Nothing there either Version 128 is still available and still has my Profile data.

Wayne Meri asked where my version 128 was located. I think it is located in C:\Program Files\Mozilla Thunderbird

Attached is an image of my profiles in the old128 version. If I click "Open Folder" for the default-esr Root Directory or Local Directory I get an error. I attached an image of the error

If I click on the default profile (the second one) I get a real file location

"default" 99.9% of the time will be empty, so that is expected. It is just a useless dummy profile.

Normally, "default-release" would have your data, even if you were running ESR. Look at "default-release" in Windows - is it empty? Or has no old files?

If empty or does not have old files, then "default-esr" should have your old data. What happens if you try to look at "default-esr" in Windows - do you get the same error?

default-release files windows finds appear to be empty except for a Cashe2 folder, Safebrowsing folder and a startupCashe folder.

Windows found a default-esr in C:\Users\lsvan\appData\Local\Packages\MozillaThunderbird.MZLA_h5892qc0xkpca\LocalCashe\Roaming\Thunderbird\Profiles.

The name is 24jytvo.default-esr