Without more information (like I advised you tho provide) I believe I can answer this (though it's a bit rambling as I have little information to work with )
Once they are recovered, and you have no more plans to recover from the old drive, you can do whatever you want with the files. The reason you don't want to recover to the source (old) drive is because any writing to that drive will reduce the likelihood of recovery greatly. Once they are recovered put them back to the drive however you wish. Unless the drive is dead/dying of course and that's why you needed recovery
(do we now see why I said provide more information?)