This is your third original post on the same issue. The abook.sqlite file is where thunderbird stores email addresses. I gave specific instructions on how to do that. Thunderbird has the menu with tools>import>import from a file to do exactly that. Be specific on whatever is your problem. And PLEASE stop writing new posts. You can reply on this thread and that is your best chance of getting this done,

How may I place the address book in the old computer into a file that may then be moved to the new computer? How do I place the address book information from the old computer into the address book of the new computer? Thanks for your patience.

If you are comfortable working with windows file explorer, you can copy the file directly. The name of the file is abook.sqlite. The easiest way to reach it on old computer is to do this: - click help>troubleshooting in thunderbird on old PC - scroll down to 'profile folder' and click 'open folder' - exit thunderbird - you are now in the profile and the abook.sqlite is there. just copy to external media - on new computer, you can do the same steps in thunderbird, but this time, after exiting thunderbird, paste the copy from external media to overwrite the copy in the profile.

With your instructions I was able to transfer the old address book to an USB. I was uncertain how to transfer the address book to the new computer, but received help from someone with computer knowledge who was able to understand your instructions and succeeded! Thank you for your help