If you want your movie clip to play frame 2 and stop frame 3, you just have to write:

if statement

event.target.gotoAndPlay(2);

frame 3 of your MovieClip

stop();

You are in frame 1. The user drags a Movie Clip named jug to a target named droptarget. So your function endDrag asks its parent (the Main Timeline) to gotoAndStop(2):

event.target.parent.gotoAndStop(2); // or this

In frame 2 another Movie Clip plays, and when it finishes to play, its parent (the Main Timeline) gotoAndStop(3). In the last frame of your movie clip:

MovieClip(parent).gotoAndStop(3);