Homebrew Can´t use Bios File With Retroarch

[KalasGiacomo]

I ´ve been trying to use a BIOS file (SCPH7502) with retroarch PSX emulator, but just can´t make it work in my new 3ds.
As it should be, i'm storing it at SD/Retroarch/Cores/system (checked in settings that it´s the directory too)
i don't know what else i should do, help me please 8(