Adding a EX8000 to a WIFI network that I already have an AX6000 on

I just upgraded my Spectrum Router and Modem to their latest models, router is a wifi 6 router.  I came back and added my existing Nighhawk extender to it, the AX6000 which paired fine.  I was thinking about adding on one of my older units I still have to get wifi to the back of my property a EX8000.  Is that possible?  Trying to even set up the 2nd one seems to be confusing my system.  Going through the standard set up it only finds the AX6000.  How to I go about finding the EX8000 to even set it up and is there anything special I need to do in order to have them both on the same network?  Thanks in advance for any help.