I do not know Mac, but this may help. Click tools>import>import from a file and follow the prompts to sqlite and then locate and select the old abook.sqlite file. That works for windows.

There are a lot of *.sqlite files in the old computer's /profiles/2vsn54vh.default folder.

I imported abook.sqlite to the new one. That added one more email contact from the old address book. I now have 2 of the contacts. There are several hundred still missing.

The MAB format was the prior version. I would repeat the keystrokes to import that as well. Otherwise, I am clueless. Good luck. If you have collected addresses, import history.sqlite and possibly history.mab

I imported abook.mab and impab.mab- and got all contacts. In all my "poking around" I did not do that before. Thanks- stress gone!

• .mab is the old format for address books in Thunderbird, so abook.mab was the old file name for Personal Address Book. Since several TB versions it has become "abook.sqlite".

There are a lot of *.sqlite files in the old computer's /profiles/2vsn54vh.default folder. I imported abook.sqlite to the new one. That added one more email contact from the old address book. I now have 2 of the contacts. There are several hundred still missing.

By default there are a abook.sqlite (Personal AB) and a history.sqlite (Collected Addresses) file in the profile folder. If you ever have imported an AB there might also be a impab.sqlite file. Which are the *.sqlite files in your old profile ? Maybe you had created an AB which contains most of your contacts instead of the Personal Address Book. Or did you create a CardDav address book with your Mac "Contacts" on the old MacBook? This would probably be abook-1.sqlite

You are very welcome. :)