Looking somehow use Pokémon bank on my New 3DS LL but don’t know how

Bought a new 3DS XL online from a guy. It was already modded and everything, has tons of games on it. What I really wanted/needed it for was completing a Pokédex in Pokémon home and being able to use Pokémon bank to transfer Pokémon from my DS games up to the Pokémon home. I keep getting the error message 005-5602.

Downloaded Luna Locales Manager but I can’t seem to get it to work correctly for my 3DS. I think the region is set to United States in the other settings and my NNID is set to United States as well. I believe the region was already changed before I got it. Can I switch it back?

Any help is appreciated.