I'm not sure what I need

You need a pre-processor and some more speakers for Dolby digital and probably a decent subwoofer. Three additional speakers and a sub will take you to Dolby 5.1. For Atmos you would need six more to get to 9.1. Good luck.

N.B. You will also need on channel of amplification per speaker. 

I should have mentioned that I plan to keep it just a right/left/center speaker maybe a sub situation.  So it appears it is a processor I need. Since I only need three channels what would be some suggestions of units that would work for me?

What's your budget?  If money was not an issue, I would probably recommend a used Krell Foundation 4K processor.  It's a 7.1 processor, so it doesn't have all the extra channels and junk for atmos stuff.  But they are in the $4.5k price range.

A used Anthem AVM-60 is in the $1900-2200 range.

I don't have a budget. I just figured the speakers were about $2200 and the amp $3000 so I should spend something similar. I will look at those pieces. Thanks.

I agree with @auxinput an Anthem AVM-60 or other used Anthem AVP that has the features/connections you need would be a great choice for your setup if in budget.