You have to use your acting instincts and your intelligence. Probably the pause in the line comes after the word "pause." Hamlet says that the thought of the dreams that may come during that sleep of death must give us pause, and then he illustrates it on the spot. He probably pauses while he tries to remember just what his nightmare was.
The length of a pause doesn't depend on the number of missing beats. It depends on the play, the scene and the actor. The purpose of the verse is to serve the play.
For a discussion of how the pause may affect the other characters in the scene, see Short Lines as an Ensemble Acting Hint.