I've never had any luck with moth balls.

I think about the best thing you can do is to set up a few mouse traps and keep checking them as often as possible.
I use cheese when I set the trap I smush the cheese onto the trap so that the mouse will have to work to get it off.
I've never had one take the cheese without getting caught, although they have moved the trap a ways away trying to get out.

Or get a cat.