Probably none of them if they want to stay in business with UPS. UPS stores are privately owned and cannot accept firearms. To ship with UPS you have to schedule a pick-up or drop it off at a UPS facility (their main hub). This is straight from the UPS website.

Firearms (including handguns) may be shipped only through a UPS Scheduled Pickup Account (specifically, Daily Pickup, Daily On-Route Pickup, UPS Smart Pickup®, and Day-Specific Pickup), or through a UPS Customer Center (counters at UPS operational facilities). Note: Firearms (including handguns) are not accepted for shipment via UPS Drop Boxes or UPS On-Call Pickup®, and may not be tendered to or dropped off at locations of The UPS Store®, any third party retailer, or any UPS Access Point™ location.

Last edited by ATC; 01/23/19.