Use the Page Break block if you’d like to add pagination, or page breaks, to a page or post. This can be useful if you are writing a step by step tutorial or if you’d like to split your page into multiple chapters, for instance.
Get started by clicking the + Inserter icon at the bottom-left corner of the screen and select the Page Break Block from the blocks list
Once you add the block it will look like this in the editor:
How it looks on your site will depend on the theme you have active. Different themes display different layouts for blocks but it will split the content after you added the Page Break block into a second page (or more depending on how many page breaks block you add