There is no one program or technique. Translating ROMs tends to require gaining some reasonable programming and reverse engineering skills, very doable but still programming/reverse engineering skills.
Beyond that the 3ds is not that well hacked, does not have well developed low level tools, does not have much in the way of debugging and does not have an emulator worth much cop. To that end you would be very much on the bleeding edge of things and that is not a good place to be if you do not know hacking in the first place, if only because you will largely have to develop your own tools and some of the lower level tools in the first place and that takes some fair knowing about what you are doing.
The GBA and DS have plenty of as yet untranslated games and all the downsides above do not exist for them (it is well hacked and documented, there are tools available, debugging is possible and there are very nice emulators available that can also assist in hacking). More on that
http://gbatemp.net/threads/gbatemp-rom-hacking-documentation-project-new-2014-edition-out.73394/
You might want to read up on GBA and DS hacking as the hardware is very similar and so are several of the formats and ways of doing things.
To answer your question though you need the ability to decrypt 3ds games (if you have a 4.5 3ds then fantastic, newer hacks are more troublesome but still doable at some level). The decryption programs will spit out a file that is known in these circles as a XORpad, it is the same size as the ROM it decrypts and is basically a copy of the ROM so people do not share them very much (and dumping teams do not include them either despite it being a good thing to do). Some decrypted games are out there and you might get somoene to share but hey.
You can also use the XORpad to encrypt the ROM again, others, including myself, would say to use so called 0 key encryption. Once that is done you will need a 3ds capable of running such things (so a gateway capable one or possible a CFW one once that gets a bit more developed, not a sky3ds or one of its clones at this stage).
3ds ROMs split down into two forms once you have that XORpad, they are known as the exefs and romfs
exefs houses the game binary which is to say the thing that sits in memory and runs on the CPU. (exefs = executable file system)
the romfs houses the game data (pictures, music, level data, text, video, 3d models, 3d textures.....)
Many games will mix and match between the two and you might find text in the contents of the exefs, back on the DS you would have found some executable code muddled in with things (definitely on the GBA) but the DS kind of separates things as a security measure of sorts.
Game data is whatever the programmers cooked up and that can be some very strange stuff indeed. "computing, learn it" is about as narrow as I can make it really if you want to be able to wander in and tackle any game.
http://www.romhacking.net/start and the docs I linked a minute ago will cover the stuff more commonly seen.
The exefs is not that well hacked in public yet and still nowhere near what we have for the GBA and DS. The disassembler is the main tool of the trade here. The 3ds has two processors though the ARM11 is likely the dominant one for things you will be doing (you might have seen terms like arm9 homebrew). I do not know what people are using for this.
About the only real positive I can say it has over the DS at this point if you are new to hacking is that the 3d subsystems and files are fairly well reverse engineered.
https://gbatemp.net/threads/extracting-models-and-textures-from-3ds-games.370788/ is a bit old but still a good jumping off point.