Look for *.mab files in your old profile. You can just copy-and paste two of them, abook.mab and history.mab. Other address book files would have to be imported using the MoreFunctionsForAddressBook add-on.

https://freeshell.de/~kaosmos/morecols-en.html

But are you aware that you could copy your old profile into your new Thunderbird and restore not just address books, but all your accounts, stored messages, add-ons, customisations, filters etc?

https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data

Where is the profile data? When I look at the backup for C:\program files(x86)\Thunderbird, there is no profile directory. There is Thunderbird profile directory under AppData, but it does not have any .mab files in any of the subdirectories.

It will be in this location: The backup may have a different profile name folder using different letters and numbers, but all should be the same on both bvackup and new computer. C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\Profiles\<Profile name>\

'profile name' folder is usually named 'xxxxxxxx.default' folder, where the x's are letters and numbers.

Image below shows location of .mab files. abook.mab is the default created 'Personal Address Book' history.mab is default created 'Collected Addresses' other *.mab files are ones you created.

You may need to make hidden files and folders visible. http://kb.mozillazine.org/Show_hidden_files_and_folders

OK, I got them. Thanks