where do I find a driver for an HP monitor?

Generally drivers are found at the device's manufacturer's website. So for an HP monitor, the HP website would be the place to look for it.

Though as mentioned, in general you should not need a driver for macOS.

In Windows, different Drivers are used for each display. You choose a setting manually in the Driver, and hope that the signal sent does not destroy the display.

MacOS uses one Driver for all displays. The Mac queries the display, asking, "what is your name, and what are your capabilities?"

Once the display responds, it will be initialized with an appropriate resolution, and should work just fine.

No driver software is needed.

A monitor does not require a third party supplied driver. What exactly is on the disc? Maybe promotional material or ...

Thanks for your kind words.

Everyone who responded to your query is a Mac User like you, who answers these queries as a volunteer, without any other compensation than making other people's computer work better, if possible.

If you need to customize the resolution, rotation, or color profile, you should be able to do so the same way you would with any other standard monitor: Open macOS System Preferences and click Displays.