Depends what type of waste and overflow assembly you have. Either way, you might want to disconnect it from the tub. Remove the cover plate from the overflow (should just use a screw driver) and if there are screws behind that holding the overflow fitting against the tub, remove those as well. Then remove the spud from the drain in the bottom of the tub. Most unscrew with a spud wrench or put the handles of a pair of pliers in the drain and unscrew it. Then move the tub as required and if the waste and overflow still line up ,reinstall it.