Depends on your specific R4 model (clones vary wildly) and goal:
.nds files (legal backups only). Place in /games/ or root..sav (auto-created) or .dsv (DeSmuME) – convert with Shunyweb Converter.usrcheat.dat in /_r4/ or /system/.Requires ntrboot or custom firmware (Luma3DS) on console to launch flashcart.
Post your cart's exact label text for precise kernel link.