Address book are .mab files I see one listed in your image.

Yes. And I should have added more information. My W10 reinstall was on or about January 21. So I'm thinking that .mab file was for the new addresses that I put there - not the hundred or so from my old address book (prior to the widows reinstall).

I do have some Macrium backups. Is it possible that some older .mab files might be there? I'm not really proficient with Macrium retrieval of files, but I'll try.

If I find an older .mab file, do I simply copy/paste it into the new Thunderbird folder?

This article explains moving address books and the file names for the 2 default books. The Personal and the Collected books. http://kb.mozillazine.org/Moving_address_books_between_profiles

I have never heard of your backup routine and would have no idea what you had it setup to backup. I guess just search for .mab files.

Other people that messed with their operating system without doing the recommend backup have found a folder named windows.old. Some of their old info was there.

Still working on this. My logic is confused by searches finding older mab files smaller than newer ones. I've attached a couple more screenshots.

My main concern at this point is copying over my current larger address.mab file with an older, smaller one. Will a copy/paste produce an irretrieval delete?? I've already messed up my address book and I don't want to bull ahead and delete my only salvation.

Rename your 2017 mab files to e.g. abook17.mab, history17.mab and impab17.mab and import them to your current profile with MoreFunctionsForAddressBook. In Address Book, Tools/MoreFunctionsForAddressBook/Actions for addressbooks/Import addressbook from mab file. That way you won't overwrite your existing address books.

https://support.mozilla.org/en-US/kb/installing-addon-thunderbird

I'm encouraged. Though I couldn't get my address book back by copying it to my Thunderbird profiles directory, I am able to open the larger 305 kb MAB file with a text editor and see that my contacts are indeed there.

Is there a utility to convert the MAB file to CSV? If I can get that then I can import my address book to Thunderbird.

Your 305 KB abook.mab is in a windows.old subfolder. Copy it into the current TB profile folder, overwriting the existing one, if you don't need the existing Personal Address Book. The current TB profile folder is opened by selecting Help/Troubleshooting Information and clicking Open Folder. Close TB before changing the profile folder.

There is no need to convert mab to csv; MoreFunctionsForAddressBook imports mab files directly.

Thanks - I finally got it. But somehow it wasn't quite as simple as instructed. Maybe it was me. But I thought I had copied my 305 kb mab file to my profiles folder but it continued to show the smaller addresses - maybe a dozen that I recently put in.

The way that I finally got it to stick was to enter %APPDATA%\Thunderbird\Profiles\ in the windows/run box as described here and it found the needed 305kb file in my windows.old directory. once I copied the file that way it brought my address books back.

Thanks for hanging with me on this. It really is appreciated.

Sorry I don't seem to understand any thing at all I am sure the times I reinstalled my Mozilla emails again it was back with all my email addresses this time I lost the lot I am not good with my computer that is why I am trown in a dark corner hope there is a simple way to get it back would it help to reinstall it?