If you copy your profile from old computer to new computer, the accounts and folders will remain the same. If you just moved individual folders, that can be problematic; move the entire profile. You can confirm where that is on old PC by starting Thunderbird, clicking help>moretroubleshootinginformation, scroll down to 'profiles' and click 'about:profiles', which will show you the exact location of the profile. Exit Thunderbird, and copy to USB stick and that can be be imported to new PC. If you install version 102 on new PC, when starting TB, click Home tab and then the Import tab to import the copied profile. If you need specific information, tell us more.

This is the first way I tried to do it and it did not work. Then I tried moving the specific profile unde the Profiles tab and that didn't work. I uninstalled Thunderbird to get a clean copy of everything and tried it again. Didn't work. I'm so frustrated because I love this email program and really need to get the old mail in there but just can't do it for some reason. And my new computer has a HUGE RAM storage and everything souped up for maximum storage and efficiency. Just not sure why this is giving me such difficulty.

Do what I recommended. If you installed current release (102), then start it and click Home tab and then click the Import profile button.

OK, I am going to try one more time. I just downloaded a fresh copy of Thunderbird to my new computer. I opened the Home page and selected import. But when I go to the Profiles folder that I copied on my flash drive, it doesn't allow me to select the FOLDER, only a zip file. So I am trying to compress the copied file I made into a zip file to import. I will let you know if that works. Thanks.

Select the top item, import from another Thunderbird installation

Back again. That didn't work because my zip file is HUGE .. much bigger than the 2GB maximum allowed. So please ... is there ANY other way I can get these folders into my new Thunderbird? I really wish that whatever has changed had been left alone. For years I have easily been able to simply copy the files into the Profiles folder and everything worked. Now no way to do it that I can find. I have been struggling with this for days now and am at a complete loss. I don't want to lose literally years of mail that I do still need as I refer back to them ... orders for my company that date back over 10 years. Believe it or not, I do still occasionally need to access them. There must be a way to do this but I have tried everything that has worked in the past as well as the suggested methods and get an error message at every turn.

NOTE: Just saw above reply ... When I tried to import the profile directly from the USB drive (as the other Thunderbird installation you mentioned), I get a red message saying import failed unexpectedly and to check error console but I don't see where that is. Anyway, if you have any other ideas, I'm all ears.