During divorce-Dad locked Mom out of house. How can she get stuff back?

I would say, you talk with your Dad & find out the reason behind his behaviour. Find out what he has to say. In marriage life problems, there's always two sides of the story. Get a common friend involved & sort out the matter, instead of just going to sort by legal ways. Going to the courts can only make it bitter & it's waste of money. However, I may add here, if no options work, then you can get legal help. I would also suggest to take help of the counseler. Thanks