Quoted from flynnibus:
The card is blank when you put it in.., game does all the formatting and loading automatically . You just need to leave a sd card and wifi dongle in each game.
However, in my case the SD cards that I had bought (and that seemed to meet all the criteria) wouldn’t finish getting formatted. I waited for maybe an hour before giving up, since it should take maybe a minute if not even less. I had one different brand SD laying around, so I formatted that in an IC machine, then read the contents as an image file on my laptop, and finally wrote that image file back to the SD cards that I had bought. They have worked flawlessly since in 6 different IC machines. I don’t know what was wrong with my SD cards originally (tried all the different file systems, FAT, exFAT, NTFS etc, tried removing and recreating partitions etc) but cloning a working one did the trick. After this operation all the machines accepted and reformatted the cards without any issues.