Step 1: First, mod your 3ds. Then you can download TwilightMenu.
Step 2: Press Start+Power to open GM9. Then insert your game.
Press A on gamecart.
Click on the .nds file.
Press A on the highlighted text.
Repeat with .sav.
Finally, go to sd/gm9/out, and move .nds to sd/roms/nds (for .sav, move to nds/saves).
And, you’re done!