AS 3.0 to 2.0

I just built an entire presentation for a client with cs3 using as 3.0. However, the client needs it to play on Flash player 6.
When I publish down to as 2.0, all my code is shot. I’m assuming the syntax is written different.

Heres an example:

pause_btn.addEventListener(MouseEvent.MOUSE_DOWN, stopMC);

function stopMC(e:Event):void{

The thing that suck for me is, I never really learned as 2.0, so I don’t know what to do to correct the problem.

Any suggestions?