for the record .... ds files are already set with the extension
.nds
if you cannot see it on your computer then your file extensions are hidden (usually by default!)
you don't have to add the extension unless you deliberately removed it
re naming ... games that are numbered have usually been through a catalogue program (offline list,RTOOLDS etc etc) that adds this number from online databases such as advanscene etc ... you can remove the number or leave it as it is
same with adding underscores
_ some people like add them some don't its personal preference ...
Alphabetically listing games ... some people insist their games are Alphanumeric ordered ... some cards already do this ... and some people have different methods of ordering ...
FAT SORT is a program that's supposed to order files on a mem card some have luck with it some have corruptions with it !? (advise use it at your own risk)
some users manually number their files 001,002,003 etc etc or add letters before the games they play most to get them in the order they want ... again its down to personal preference
Personally I use SAKURA with my M3 REAL it orders them Alphanumerically along with its ability to show the last 5 or so recently used games/applications/homebrew in a quick access menu