Follow the instructions to move your profile. https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

This idea doesn't work because when I click the "Open Folder" button, the NEW version files display. I need to transfer files from an earlier installation to a new one on the *same* computer.

Apparently, the new version over-wrote the old one and maybe zapped the mailing list files.

The TB mailing list I need is titled "Contacts." I have a backup folder labeled Contacts.sbd. Even if it is an inbox folder, it would contain the info I need.

Can I copy it to the new installation to recover it? If so, where?

Thank you again for helping me, Anna

If your mailing lists were in the Personal Address Book, you can import the old address book by copying abook.mab into the new profile folder, while TB is closed. If your current PAB is needed, rename it to abook.bak before you copy in the abook.mab file.

I copied the old abook.mab file to the new profiles folder. Nothing happened. I searched for other .mab files and found only history.mab with a recent modification date. It looks like I'm outta luck and must rebuild from scratch [OUCH!].

I am grateful for your kindness and conscientious efforts to help me, Anna