You can import your messages from the .tbb files (every folder has its own messages.tbb and .tbi files) by picking from the menu:
Tools -> Import messages -> from TB message base v2 and browse to your selected folder.

Another option would be to install TB, tell it you want to create a new account, pick the mail directory that contains your accounts and next create new accounts with the same names as your old accounts. TB will use your previous settings, filters, templates, message base, etc.