Non-acid rust remover is the place to start. But if the filing cabinets have been in place a long time, the rust stains may be rather deep. You will need an acid to remove the stains. Then you need to repolish the floor to remove harm done by the acid. Depending upon condition of the floor and desired level of gloss when you are done, this may be accomplished with Spinergy / Monkey pads or you may need to go to resin bonded diamond discs.