Do you have the ability to dump the rom using gateway menu? If you can recover the header, you can restore the header to a retail rom and manually inject the powersaves save into the a rom using cart2sav. (of coarse you have to remove custom header that powersaves adds to the save first)
However if you can't recover the header to the game and save data filer does not see the cart, your save is gone forever.
This requires you own a Gateway otherwise you won't be able to load the rom into slot-1.
CIAs do not store saves the right way so you can't transfer the save to a CIA of the game unless you have a way to boot the 3DS file.