A mod is like a midi in some ways, is a sequence of samples played at the right time, so, you have 5 samples, you compose tracks, and then you play them in order, and you have a mod.
You can't simply do that conversion, but you can take samples from that song, parts that repeats, like the rithm or something like that, and take some samples from another place and write a song that sounds like the wav (or almost)