What exactly is a QDRO and how do I get one for my ex’s pension?

In my divorce the judge awarded me part of my husband’s pension. My lawyer at the time said I needed to have something called a “QDRO” to get my share of the retirement payments. I wasn’t happy with the way the lawyer handled my divorce and no QDRO was ever done. My ex is receiving his full pension every month and I’m not getting any part of it. I’ve researched how to do one myself and they seem very complicated. Every month that passes I’m being cheated out of my fair share of the retirement. I’ve asked my ex to pay me my share directly and he says he won’t until the law requires him to. How do I go about getting a QDRO and my retirement payments?