Help - Extracting content from .dat files of the ROMFS and repacking them

Hello , i am new to this website. Im happy to join.

I recently was able to extract the files of Mario Sports Superstars , however , the game seems to be heavily compressed as the romfs folder (the one that contains all the data) contains most files in DAT files.

I have no idea how to open these files and i have researched a lot with no luck. 

Here are some screenshots of the folder.



I am almost 100% sure that ''na'' folders , contains the game's sounds and music , which is what i want to rip first.

I would also want to know if there's a way to repack the files after being extracted.

If anybody can help me with this it would be amazing.