I need help finding this movie title? Easy ten points?

I saw this really popular movie for kids a few years ago, but I forgot the name. All I remember is that it's a cartoon about two mice that go save an orphan girl that was kidnapped by an evil woman that lived in a swamp with alligators and that is forced to dig in a mine for a large diamond. When she finally finds the diamond, the mice help her escape, and the little girl is adopted into a family. I'm pretty sure the name of the girl was Penny. The movie was really sweet and I'd like to show it to my little sister. Please tell me the name if you remember the title.