Was that one of the ones with all the files in the overlay directories? As in many hundreds of the things rather than say 20.
If so then you have encountered one of the hard ones. Pick another if you want, or be prepared to spend a lot of time ploughing through it.
If not, or perhaps in addition to, and everything is just named .bin then do check to see if the files headers themselves give indications of the file type -- more than once I have seen files be named.bin but actually be a known format (the system Nintendo uses has no obligation to use the names if the dev does not want to). If you need a basic overview of the well known formats then
https://www.romhacking.net/documents/469/ and things don't tend to get named for the extension as much as the magic stamp.
If they are all mostly custom formats then you get to figure it out however you will like ROM hackers on systems before you that did not have file systems (though with some of the benefits of a file system) -- analyse the files to figure out what they do (they might all be .bin but most devs will reuse the same format over and over within the same game), scan through them with various tools (open in tile editor, choose settings, press page down a lot), trace back things (that will be the B7 commands in
http://problemkaputt.de/gbatek.htm#dscartridgeprotocol , or you might be able to go a level back and figure it out from what the DS ROM looks up), corrupt files and see what changes in the game (can also eliminate other files), compare between regions to see what changed (in your average translation it is most likely text, font, possibly voice over and maybe some light censorship of certain characters or concepts where everything else is essentially the same. If you know what has changed and what was changed in the final game you have a good idea of what goes) and all the other basic analysis tools we have (things like size -- a 10 byte file is probably not going to be a nicely detailed background image).
