quick MAME question

[FS]

I came into the MAME thing rather late (since it took me long to finally get a decent pc) and now I just need a little help to understand how this works. Right now I have only one working rom, Mortal Kombat 3.

I'm trying to get my hands on Street Fighter 2 the New Challengers (or World Edition, I forget because there's so many fricking versions) by downloading from romnation.net, only files for the version I'm looking for are all under 1 MB, and in my limited experience, roms are like 70-80 MB usually. How does this work? The zip file contains some files with numbers, not .bin files like that one rom I have came with. What do I need?