Best answer ever from
@SciresM :
https://gbatemp.net/threads/questions-i-want-to-translate-roms.396597/#post-5653058
Understanding the steps is a requirement.
Then you can start learning/working on each step individually, but you can't just start translating whatever you want right away.
Every game are different, so there's no simple and unique tutorial. it would require a tutorial per game, and if a game already got a translation there's usually no need to make a tutorial for it.
Starting with 3DS is maybe not the easiest to understand and pick your first translation project.
old consoles didn't had encryption layers, so it was easier. (not easy, just less steps to extract the files ... when files existed. Not all consoles or games have a file system)