The process to format an SD card to FAT32 is different for each operating system.
Choose your operating system
If you have a 3DS with custom firmware, you can also use GodMode9 to format an SD card to FAT32:
The process to format an SD card to FAT32 is different for each operating system.
If you have a 3DS with custom firmware, you can also use GodMode9 to format an SD card to FAT32: