importing (archived) TB mail to Mac Mail?

i have a large amount of old email that seems to reside in thunderbird profiles which i think i transferred when i moved to the mac many years ago. right now they exist as about four email profiles in thunderbird on my mac.

i would like to make an attempt to get all this organized and am considering importing this email to Mac Mail.

are there any power users that can suggest an easy way to do this or to alternately suggest a way to ARCHIVE older mail so it is easily accessible?

THANKS