Do these mount at factory holes or do I need to drill?

These mount at factory rocker and suspension points — no drilling required. You'll use existing attachment locations on your vehicle.

Does the silver finish need any prep before install?

The powder-coat is ready to install as-is. If you're concerned about any shipping scuffs, light touch-up with automotive touch-up paint works fine before bolting on.

What hardware do I need to bolt these on?

Hardware is not confirmed as included. Source fasteners that match your factory mounting bolt pattern and gauge — your vehicle's service manual will specify the size and torque spec.