Before you do anything, backup your save games by following this https://gbatemp.net/threads/importing-gateway-saves-to-cia-games.425743/
You'll be able to install JKSM by using FBI.3ds from your Gateway card to install JKSM.cia
Then, follow https://3ds.guide
You'll be able to use either the browser if you have one, or MSET (similar to how you install the DS profile exploit for Gateway).
- Reboot the system, then go to System Settings, then “Other Settings”, then “Profile”, then “Nintendo DS Profile”
- If the exploit was successful, you will have booted into SafeB9SInstaller
SafeB9SInstaller.nds is on DS cart.
boot.3dsx, SafeB9SInstaller.dat, boot.firm all on SD Card. As well as boot9strap folder with two required files inside.
Firmware is 4.4.0-10u, so I downloaded the 4.0 to 4.5 Installing boot9strap (MSET).
Also my NDS flashcart is a blue gateway.