By default the SharePoint ‘Get Items’ connector (in Logic Apps & Power Platform) only return 100 items.
If you want to get more items, but know the number of items is less than 5000, you can put that number (up to 5000) in the Top Count field.
Can’t go above 5000.
You can get more by clicking on the 3 dots > Settings > Pagination > and entering a number here.
The maximum number here is 100,000 (you get a warning when putting a number larger than that).
While Googling on this I also came across this and this blog posts. They (especially the second one) go into exhaustive detail.