Insert your SD card into a computer. Navigate to the gm9/out/ folder. Inside, you will see a file named [serialnumber]_sysnand_###.bin accompanied by a .bin.sha verification file.
If prompted to restore your original console unique files (like local friend codes or keys), press to accept. Installing and Setting Up a NAND for Citra Emulator 3ds nand download install
The 3DS internal NAND has limited space. Only install essential system apps to [A:] SYSNAND . Use [0:] SDCARD for games. Insert your SD card into a computer
Copy your personal backup (the .bin file from earlier) from your PC to your SD card’s root or a gm9/out folder. Put the SD card back into the 3DS. 3ds nand download install