@bothump1,
Welcome to HP Forums, this is a great place to get support, find answers and tips.
Thank you for posting your query, I'll be more than glad to help you.
I understand that you are unable to find the drivers for your HP OfficeJet 7210 All-in-One to work with Mac OS El Capitan.
As the printer is more than 10 years old the drivers may not be available.
However, you may try to add the built-in drivers from the Mac update from the link: Installing a Mac Printer Driver Using Apple Software Update
Let me know how this works.
You have a good day ahead.
Rainbow23 - HP Support.