Stopping a child support order

My child and I live in NJ and my ex-husband lives in PA. He was ordered to pay child support after our divorce in May of 2008. He hadn't paid a dime of it for over a year when they finally started to garnish his wages for the monthly amount as well as arrears. I have since gotten remarried and my new husband has just adopted my 10 year old son. How do I get them to cancel the original child support order now that my ex-husband is no longer my child's father in the eyes of the law?