First things first... tell us what you know about the format. Which game is it used in, if it works on in_cube. What you have already tried to do with the file.
It's a bit unfair to drop a file extension into the thread and expect us to know what it is without any other info.
Well, it came in the game YuGiOh: The falsebound kingdom, I tried it at In_Cube and It doesn't work
The only dead I have about that format is that is some type of Packed file judging for the extension ".pac", that contains all the sound and music files inside it, but it don't comprehend how to "unpack", if there's some way to do it
Sorry for my first undetailed post but I was about to go to sleep
Hmm, I could swear I'd heard of this game, and dealt with the .pac files, at some point in the past... Ah, Here's the thread. Looks like he just lost interest. As mentioned there, the best strategy is to put some of these files online and let me take a look at them. If it is impractical to upload all of the files (.PAC, .MRG, .GRP) could you maybe upload just a set of similarly names ones, or provide a list of file names for me to select from?