Finder

Please refer to Change General preferences on Mac - Apple Support:

"Recent items

Recent Items you’ve used are listed in the Apple menu, so that you can easily open the items from there. Choose how many items are listed.

This setting also determines how many recent items appear in app menus, such as the File > Open Recent menu in TextEdit."

Upon further reflection regarding your question...if you are referring to "Recents" in the Finder Sidebar, I don't know how to control the number of recents displayed in that location. In my first post, the Apple Support Article link only refers to the setting which controls "Recents" as displayed in this Screenshot: