How do I get TB emails from my old disk to my new disk. File transfer is missing.

My original disk lost its XP Pro, so I got a new PC. I can still access most files on my old disk, as it is now attached via an external enclosure, but I cannot find how to get access to my old Thunderbird inbox. "File Transfer Wizard" is missing, and MS Search is broken and won't start. T'Bird works fine on the new disk/PC, but I need to look up some correspondence on the old disk. Is there some file I can point T'Bird to, that will contain my old emails ? Can I somehow merge the old and current files so I can search on a subject or person ?