Was going to say something along the lines of this originally. It's pretty baffling that you couldn't find it yourself but with the quality/nature of all 3DS related threads recently it's easy to get used to stupid threads like this.
Mate a headphone jack is a headphone jack hahahahaha. You all have ipods, cd players, old DSs/whatever else that have them. It should not be difficult to find one on a small rectangular device that fits in your hands. Manual shouldn't even need to be consulted.