Nintendo of Japan is going to start releasing previous 3DS games on the Nintendo 3DS eShop like Super Mario 3D Land and Mario Kart 7. If you happen to want to purchase the digital copy of the game and you already have a physical copy, Nintendo is making it so you can move the save data from the retail game to the digital one. Nintendo is going to release some sort of tool in the Spring for Japan so this file transfer can go through.