Is there an emunand on the Sd card?
if so,
Try reinand since it's easiest.
Put this file in the root of the sd card if your arm9hax doesn't have screen init:
https://gbatemp.net/threads/source-release-reinand-n3ds-cfw.394309/page-193#post-6080515
If you do have screen init:
https://github.com/Reisyukaku/ReiNand/releases/download/v3.3/ReiNandv3.3.a9lh.zip
Finally, you also need these files/folders on the root of sd card with either option above:
https://github.com/Reisyukaku/ReiNand/releases/download/v3.3/ReiNandv3.3.zip
If you boot up then you're good to go- update your emunand if needed!
Also: I live in USA/Chicago and hard modded my 3ds xl twice from bricks. It was a temp hard mod so I removed the wiring when I was done. If you want a perm hard mod access port id suggest working with someone else.