Samsung and Android updates have been known to move or remove carrier-specific toggles. If you cannot find the "Hide Caller ID" option on your S9, U.S. Cellular can enable this at the network level.
Once selected, exit the menu. Your Galaxy S9 is now set to hide your number for all outgoing calls. The person receiving your call will see "Private," "Anonymous," or "Blocked" on their screen instead of your phone number.