How to get urine out of mattress?

My 2 year old has ripped off her mattress protector multiple times and has wet the bed (even in pull-ups) multiple times. Her mattress smells horrible of pee and I can’t figure out how to clean it. If we can’t clean it, she won’t have a bed. It was a $100 mattress but we can’t afford one right now since my husband just lost his job.