@JohnHeisler, welcome to the forum.
Here is the Service and Maintenance Guide for the computer. On Page 19 you will find the rear panel components. You should read the Note: at the bottom of the page. I believe that you should be able to use three monitors, since there are 2 DisPlay ports and a VGA port. The problem with this option is that the VGA port is analog, not digital. Also, you could use a USB 3.0 video adapter to add the monitors. StarTech makes many different versions. If you like this option, you can use their Chat Live option to talk to one of their Techs. They can help you choose the best adapter for your needs.
Please click the Thumbs up + button if I have helped you and click Accept as Solution if your problem is solved.

I am not an HP Employee!!Intelligence is God given. Wisdom is the sum of our mistakes!!