To secure the title, he needs to score at least three points this weekend. Three points means even if Prez manages to get the maximum points in every event, Verstappen will still take home his third title.
Verstappen will become the first driver to clinch a title in a Sprint race if he finishes sixth or higher (three points or more) in the short-form format on Saturday. That is irrespective of where Perez finishes. And, in any case, if Perez does not finish in the top three of the Sprint, Verstappen is champion anyway.