I think this thread addresses your issue of importing contacts, assuming you have a csv file.

 See   https://support.mozilla.org/en-US/questions/1569866

My problem was not resolved. Maybe because I was trying to import a file named "122916_Backup Contacts.pst". My computer froze up and I had to force a shut down. I also have another smaller file named "122716_Outlook.pst". Should I try this one ? I have a license and software product key number for MS Outlook 2010 and the last time I tried to purchase a more recent version, I only got a monthly premium option. I retired on July 31 of 2009 and running out of retirement funds. I have been reducing my monthly budget to preserve my 800 plus credit score so I don't need another monthly bill.

First, I am not familiar with all the details of importing Outlook, but my understanding is that Outlook must be installed on the same PC for the import to work. Otherwise, you need a third-party tool to convert your pst file to one that is compatible with thunderbird.

I see. I do have the Window 11 version of Outlook but I was trying to import the contacts file from or while in the Thunderbird email. I'll try importing the file opening my outlook. Thanks.