ac chargers never been apart of the box when you purchase an apple watch
Apple Watch Ultra 2 - Technical Specifications - Apple
In the Box
- Apple Watch Ultra 2
- Band
- Apple Watch Magnetic Fast Charger to USB-C Cable (1m)
you can use any ac charger that is 5watt or higher and if the chargers you have only have usa-a rather than usb-c then you can get an adaptor Amazon.com : usb-c to usb-a
or purchase a usb-c chager Buy 20W USB-C Power Adapter - Apple
about pre-owned then one of cause has to be careful it's not a stolen device with an activation lock and or that the battery health is not getting close to 80% in which case one will need to replace it