You translate 3ds games more or less like you do for other file system using consoles. The main exception is the 3ds hacking scene has a tool called hans which allows you to apply patches to games/swap out files and such so you can effectively hack an original game.
Translating to Arabic is not the easiest task either. I am told we can leave the joined up stuff in computers and just have characters which is fine. Right to left is a different matter though. There are two main approaches, 1) is put enough spaces in that you can treat it as right to left (the somewhat recent Zelda Ocarina of time hacks did this, which is why they tend to favour the French versions of games apparently as they have the largest script in the first place) , and 2) is actually hack the game to do right to left text rendering which is not the hardest hack (some of the variable width and line alignment stuff taking that crown) but not a trivial one either.
"ps: if I have physical copies of the games can I also translate it and how can I put it in my pc?"
If you mean can I dump ROMs then yes you can. If you mean can you play it on your PC then some people are working on emulators, the main one being called Citra.
http://gbatemp.net/threads/citra-new-3ds-emulator.365154/
It is not suitable for play, it is not terribly suitable for debugging/hacking and about all it could do right now is take a very long time to make a screenshot (which you could also do with a hacked 3ds).
Regardless of what you do you are going to want a hacked 3ds that is capable of running custom code. There are a bunch of guides to it all on the forums, here is a good place to start
http://gbatemp.net/threads/3ds-noob-paradise-ask-questions-here.359035/ . Things have just about tipped these days and custom firmwares are the chosen/preferred method. Until somewhat recently you might have been better off getting a flash cart and they do still afford certain bonuses but custom firmwares (and installing the games as CIA) will allow you to pretty much do it all.
https://www.3dbrew.org/wiki/Category:File_formats has a bunch on some of the 3ds specific formats you might encounter, and is probably also the main reference for the 3ds hardware. After that it is the same as it is for most systems and you can read things like
http://gbatemp.net/threads/gbatemp-rom-hacking-documentation-project-new-2016-edition-out.73394/ and
http://www.romhacking.net/start/ to get started there.