Another angle is the availability of emulators for DS. There are emulators like MelonDS that can run NDS games. The user would need the original rom and the emulator. But again, the legal aspect of obtaining the rom is key here.
If they don't own the game, then advising is needed about the legal aspects. However, if they do own it, they can create a backup rom legally in some jurisdictions, but it's still complicated and region-specific. Mario Kart Ds Gamecube Grand Prix Rom Download
Additionally, the user might be confused between the Mario Kart DS and Mario Kart: Double Dash!!, which is the GameCube version. They could be mixing up titles. It's worth clarifying that Mario Kart DS is for DS, not GameCube. So the "Gamecube Grand Prix" part might be a misunderstanding or a mix-up. Another angle is the availability of emulators for DS