If you are just reading files, it doesn't matter what type they are.
If you want to decode an MP3 file and play the music, that will be much more complex and is probably too much work for an HCS08 MCU.
You can use another chip like STM STA013 to decode the MP3 file with help from the HCS08.
In order to get help reading files, you need to explain how the files are stored - on a hard drive, Flash memory card or chip, CD rom etc. They all need different hardware and software.
Good luck
