Convert all the mp3 files into wav files first then try the above
I do mean convert not rename
If you don't know of any converting software try LameDrop I think it was, install and then drag and drop all those mp3's onto it
Edit:-
LameDropXPd
MP3's are used just to make the download much smaller but can't be used directly like that in most software so need converting back into WAVE format *.wav to be usable, you don't realy need to convert those into a bin+cue, once you have all your *.wav files instead of *.mp3 you can mount the WAVE cue in Daemon Tools and boot up SSF, and the game will then either just work or will show a message saying this disc is not designed for this system, if you get the error message then just change the region settings and then ok it and finally restert the emu.
ISObuster may be optn the mp3 cue sheet directly but I don't remember off the top of my head, but that software can convert to bin+cue directly