I need to know if my ex filed for bankruptcy and in our divorce decree it stated that he was to pay certain debts that I was a co-signer on, am I responsible for that debt when he files, and doesn't he need 4 years of tax papers to file?

If you are a co-signer, then, by law, you are equally responsible for the debt. The divorce decree, though binding on you and your ex-husband, but NOT on the holder of the note.