The SuperCard SD is a flash cartridge solution for the Nintendo GameBoy Advance using a Mini SD card.
I had my Mini SD formatted as FAT32 but that is not supported, you have to format it just as FAT otherwise you will see this message:
You have to see the menu :
Information:
https://www.minihere.com/supercard-mini-sd-gba-flashcart-firmware-v1-85-software-v2-71-download.html