ask dr LJ

So I just bought a replacement for my aging and dying MacBook Pro. One would expect an easy transition here, but 1) I had software that I did not want to transfer and then 2) migration assistant didn't work at all!!??? which is a big WTF, seeing as I asked it to migrate all my documents, but not my apps. So I've transferred all my documents and installed new the software that I do want. But I have this one little (ok, really huge) problem. I can't find where thunderbird has stored my email so that I can transfer it. We're talking thousands of emails, about 500 of which I do really NEED to keep. Spread out over 5 addresses and sorted and stored in several dozen folders.

HELP?