how rare are these
 

I have somewhere a original ninja turtle cassette of the soundtrack and at a pawn shop seen they have TMNT 2 Secret of the ooze behind the seens(misspelled) How rare are those items?

The cassettes aren't that rare. I've got a case of about probably 50+ TMNT soundtrack cassettes that were only a few cents each.

I have never seen Secret of the Ooze: Behind the Scenes with Scenes misspelled so it might be worth picking up if it is reasonable. I don't know if it is even real. I have seen similar things overseas in Bangkok, and China that had misprints, and I bought them only because they were so cheap, but they are definitely not officially produced items. Might be worth taking a look though

They're not that rare. I picked up the first and third TMNT movie soundtracks on cassette at Goodwill. I also see the TMNT movies at Goodwill quite frequently, including Behind the Scenes of Secret of the Ooze.