i bought a new psp memory card and i can\’t put my games?

*i already formatted the mmc (my psp is the psp slim)

-when i connect to the pc there’s 5 files (MP_Root,Music,Picture,Video,PSP<GAMES( is under PSP folder)

- i don't know anything about the firmware and custom firmware thingy thingy. so please don't tell me that i need to get custom firmware (first of all, what is custom firmware?) [please tell me something like, "you need to get firmware 5*.** at this site.. etc." - Thanks alot]

-my system software says: Version 5.55

i tried putting on my cso game on the GAME folder under PSP, but when i disconnect the usb it doesnt appear on the games on mmc.

i also tried creating a folder ISO and putting my game there, but it still doesn't appear

i was able to put & play games here before, but i don't know what happened.. and i think my system software back then was different. also, i broke my former memory card that's why i bought a new one.

thanks alot for the help