View number of items in a folder in Icon view
This option is called "Show item Info" and is toggled from the View menu rather from Preferences.


Select the finder window you want to apply this view to, even the desktop. And set it to icon view.
Go to the View menu and select "Show view options."
A window opens up (like below) check the Show Item Info checkbox.


Now folder icons will show the number of files in them for that window.