Are the graphics the sorts of the thing you might be able to get during normal gameplay?
If you are new to this then that is often the easier, if more long winded method. Here you play the game but in the emulator you have VRAM viewers, tile viewers, BG viewers, sprite/OAM viewers... whatever your chosen emulator (desmume and no$gba will both have them, I imagine melonds will also have something) open and grab images you want from them as they appear. By all means use cheats, turbo button, unlocked saves and the like to help speed things along.
If not then you get to play ROM hacker and the Phoenix Wright series is one of the harder options to start out on (if you have seen a sprite sheet for older games and seen just the 50 different takes on the eye section be on it then that is what you get to look forward to. You will probably have something similar with just the in game tile viewers but they will also be fully coloured).
SDAT is the sound file in most DS games (there are a few that use other formats or additional sound formats). .bin is a generic extension (short for binary) that is used across computing and has at least 3 notably different takes in just about every DS ROM out there (ARM9.bin is the thing the CPU runs, ARM7 another, overlays another), here probably more than that and also those mentioned in the bracketed bit can include the data you want.
Anyway graphics are usually seen with a tile viewer. Crystaltile2 is probably the best one around for DS purposes, though some come close. Tiles are just a paint by numbers affair and you have a palette to determine what those colours are (hence the term palette swap for older games where you see the same image but with some tweaked colours and they call it a hobgoblin rather than just a plain goblin). You can rip a palette from an emulator if you like and skip finding where it is stashed in the game files (assuming it even is and is not generated/altered on the fly) whilst still using a tile viewer. Said tile viewer will probably also want custom size tiles compared to the usual 8x8 or 16x16 that most games will be using, though they could have made things simpler in this game (I doubt it as I did have a word with someone doing the translation a while back and it had some tricky aspects for the graphics).
