there is no first episode , i got confused to at first but the reason they did that is because the guy that played chef quit so they hd to do a last episode for him

ya the actual episode where he leaves doesn't exist. The "previously on South Park" that they do at the beginning of "The Return of Chef" is totally made up for that episode. Isaac Hayes quit the show on short notice because of the Scientology episode, so that why "The Return of Chef" is just funny, out of place, old voice clips for Chefs lines. You can check out all the info here:
http://en.wikipedia.org/wiki/The_Return_of_Chef

There was no episode where he left. That confused me too. The only episode involving Chef and the Super Adventure Club was "The Return of Chef."