Hello,
select the last frame of your movie clip, enter a keyframe there if it's not
already(to insert a keyframe press F6).
then select the keyframe, and press F9 (for the action panel to appear).. then
if you want the movie to go to that frame and stop there enter this code:

this.gotoAndStop(13);

if you want the movie to go at that frame and then play from there enter this
code:

this.gotoAndPlay(13);

* 13 is the frame number, enter you own....


this.gotoAndStop(13);