If both versions of Thunderbird are recent, the file is abook.sqlite and is in the profile folder. Just copy from one PC and store on the other. If the older PC's version of Thunderbird is older than version 76, then the address book might be abook.mab. In that case, copy from old profile and store in profile on new PC. Then, start TB and click tools>addressbook and then click Tools>Import>addressbook>mab. If you're unsure where the profile it, it can be found using File Explorer at c:\users\yourID\appdata\roaming\thunderbird\profiles\yourprofilename.

Thank you. I found the file on my old computer but it won't upload to One Drive, so I can't download it to my new computer. I've found the place I need to copy it to & everything. So frustrating. I've even connected my computers by Bluetooth & cable but can't transfer b/c Windows Explorer or whatever doesn't acknowledge the accurate password for connecting each computer!

I appreciate the help & understand what I have to do to get the address book. I just wish I could actually do it.

Any chance you could email it to yourself and then download on new computer? Do you or a friend have a USB stick? It's frustrating, I'm sure.

Finally got One Drive to work by discovering I have 2 Microsoft accounts! Geesh! File had uploaded to one & I was looking at other. Thanks so much for your help!! Can you tell me the name of the TB file that has all my email folders in it so I can transfer THAT file as well? I think another conversation here stated to move the entire profile folder??? Thx again.

Your old PC should have a folder at c:\users\yourID\appdata\roaming\thunderbird\profile. That folder's name probably ends with 'default' or similar. That is everything, including your old addressbook. If TB is already installed on new PC, there will be a folder on new PC with the same naming structure, although the userid will probably be different, e.g., c:\users\xxxxx\appdata\roaming\thunderbird\profile Copy your profile into the same location. There may be another profile folder there, but it's just the dummy one that TB inserts on a new install. Ignore it. Now, start TB. It will prompt for an email id. Ignore. Click the 'home' tab and then, in upper right, right-click and activate menu bar. Then, click help>moretroubleshootinginformation. Scroll down to Profiles. Click 'about:profiles' and you should see your profile listed. Select it and you're good to go. Let me know how it goes.

Thank you David. All makes sense. Now trouble downloading from One Drive [tells me there's trouble but doesn't tell me why]. I may resort to using an external storage as you previously suggested, if I can't get this to work. Thx for all your great help.

I had a pretty old version of TBird so needed to import the *.mab file. I had a TBird backup done by the computer guy, but can't find my own backup. Old Computer had 3 address books & some mishmash - mostly addresses from about 10 years ago - got transferred to New Computer & it doesn't include my main address book. Old Computer is pretty unstable (CPU fan problem) so I probably can't keep it on long enough to find & back up the old address book. Am I out of luck? [at least the emails / history transferred]

thanks for any help anyone can give me.

Can you do a screenshot of the computer guy's backup, viewed from File Explorer? That will help in assessing its completeness.

here's part of it, which includes all addr files in the folder - i only know how to do prtscrn & open that in Paint.

pat

PS okay this is crazy, it's hanging when trying to upload a *.png file that's less than 200K. I don't have much patience. Is there a list somewhere of what should be in the folder relating to the address book? all the folder had was abook.mab

Looks like I'm just out of luck on this issue. I can't get the PNG file with the screenshot of Computer Guy's profile backup to upload.

If I can get TBird to open on my old laptop (no success so far, it can't find the profile) or if I ever get the old computer with CPU fan issues to open I might be able to export the address book somehow or at least see what's in it. I have an abbreviated address book in online Outlook but the stuff TBird imports is trash, just about as useless as what transfers from the MAB file.

Your old profile is probably at c:\users\yourID\appdata\roaming\thunderbird\profiles If Tb can't find it, you can right-click on the Thunderbird desktop icon and add -p to the target line so that it's to the right of "...thunderbird.exe" That starts profile manager and from there, you can click 'create profile, click next, enter a name, e.g., MYPROFILE, and click browse to select your profile.

i think i've parked a copy of the entire profile on the laptop's desktop, so no problem there -- though i'm pretty sure it's in user/appdata etc where it belongs. but pointing at the computer & saying "it's right there!" doesn't seem to work :-)

the missing piece is your very useful tip about -p, which i used on New Computer to point TBird (& maybe FFox too?) at the correct profile & promptly forgot about.

So at least now I can look at the old address book & make notes about what's there.

Thank you!