I just got this honda atc, I'm not sure ehat model it is but its a chain drive and I'm pretty sure its 200 engine, but I don't know where the oil drain is, its not under the engine, so it must be on the side, but witch one?
help

 

On the left side right below the recoil starter. It's a drain plug cap that also happens to be the same part as the valve cover caps so it's easy to find. Don't lose the strainer screen when you drain the oil and be sure not to over tighten the cap when you are done as it doesnt take much to damage it.

 

is it the BIG one, the one that is like half an inch or an inch, very different then the others, that one?

 

There is only one drain there. The cap itself is IDENTICAL to the two valve adjustment caps on top of the engine if that helps you any.
Look below the recoil starter and the drain cap is right there on the side of the engine case... right in front of the shifter shaft regardless of which 200 model you have.