If you want to use a different format for the slide numbers, then a great way to apply the format to all the slides (existing and new slides) is using the Slide Master view. Customizing the Slide Numbers in Slide Master View If you need to start with a different number, you can specify the start number in Starts at textbox. In some presentations, it is not desired to include a slide number in the first slide that is used as a cover slide, for instance.
Also, you can check Don’t show on title slide, to prevent displaying the slide number on the cover slide. As you can see in the picture below, we have checked the Slide number checkbox and entered a Footer text.
Here are the options where you can customize the slide numbers in Header and Footer.
