Mostly stuff about the filesystem and procedures I use to get assets. If you want to jump in, get a 3DS/2DS and follow https://3ds.hacks.guide/.
The procedure starts on my softmodded 2DS. I have an 8 GB microSD card that I use with it for transferring dumps and homebrew. GodMode9 takes care of ripping from the game card. The microSD card then goes into my laptop where I load it onto an external hard drive. That can be opened in the Citra emulator which is where I dump the filesystem. This filesystem will contain some sounds and video clips, but if you want to go further, you'll need 3ds-xfsatool. If you're not interested in compiling stuff, use Kuriimu2 (seems like it's Windows-only at this stage, other ports are broken).