I had some music writing software that would pull in a midi file and then show the score for all the instruments on screen.
I'm going to go out on a limb here and assume you want to learn to play the cajun accordion by reading music. I know this would seem like an easy way to go, but there are drawbacks. They keyboard layout does not lend itself to this.
If you're looking at some of those MIDI files created by "The Accordion Man", you should be wary. Plus, there's a bunch of "tricks" they throw in there to try to emulate a cajun accordion sound it seems, resulting in lots and lots of instruments that you wouldn't normally see. Makes it hard to sort out what it is you're supposed to be playing.
The music is already scored out in two books that are available on the market: "Cajun Music: The Story of a People" by Ann Savoy, and "Ye Yaille Chere", can't remember the author's name.
However, what is contained in there is usually the basic skeleton of the songs, without all the ornamentation that an accordionist would play. Or the octaves.
If you're going to try to play a cajun accordion by reading music, good luck. The keyboard layout does have a logic to it, but it is still illogical as far as your fingers are concerned.
You really are going to have to sit down with the box, and with some recordings, and try it by ear. This is a "by ear" instrument.
Also, finding people who can help you get started, who already know some of the songs, or how to play a diatonic instrument, will help get you over the hump.