I am playing a game on my phone called Final Fantasy and I want to transfer the save file to my Nintendo 3DS because I don't have enough storage, but I want to keep the save. Is this possible? If yes, how do I do that?
If you're trying to transfer your save to a 3DS version of the game; Not possible.
If you're just trying to back up your save, using your 3DS's SD card:
Figure out where FF keeps its save data, copy it to your SD card using either the two methods mentioned above, or via a computer.