Hi,
please follow the below-mentioned steps carefully.
I hope this method will help you to import the contacts from Google account to Thunderbird.
1. Sign to Gmail account & select Contacts
2. Go to Menu click on More & go to Export
3. Select the contacts that are to be migrated
4. Now, from Menu >> More option >> click on export.
5. A new dialog box will be appeared to Export Contacts, click on All contacts
6. To import the address book from Gmail to Thunderbird open Thunderbird
7. Choose Address book & then Open Mozilla Thunderbird Address Window
8. Click on Tools >> Import tab >> & Go to Address books from the options
9. Now, click on Next.
10. In the new wizard, choose Text File and click on Next.
11. In the new window attach the path directory, where the stored Gmail address book is located
12. Choose All Files to view the CSV file
13. Click on OK
The migration process has completed successfully. Now, check Thunderbird address book