One of my mollies gave birth too, she let go of 5 babies and then about 14 hours later gave birth to the rest, let her be in the breeding box, just make sure you leave her alone because if you stress her a lot she will give birth prematurely.
She has a lot more babies on the way, so just leave her in there and tonight you will probably find a bunch more molly babies
I ended up with like 20 babies. I am keeping one and the rest are going to a local pet shop that said they would buy them. So shop around for one of those like small pet shops and you may get paid!