Whenever I boot up GCMM and try to restore, it has the file on screen but it says memory card not inserted. I tried selecting slot a and b but it never works. I have the SD card in the Wii but it never registers the SD card in the Wii.

GameCube games don't save to the SD card, they use the specific memory card slots on the top of the Wii, next to the controller ports.

Okay thanks! :)