WEP

WEP is a wireless security mode that is seen on wifi routers. The CM1000 is a modem only. No wifi or router here. 

Is your Wifi 6 mesh system a Orbi AX system? What model Orbi RBK system do you have? 

> How do I find my WEP address on a CM1000v2 (or is it on my Mesh WiFi 6
> system?

   Do you mean "MAC address"?

      https://en.wikipedia.org/wiki/MAC_address

   Every network interface has a MAC address, so you could find one (or
more) of them on any networked device.

   WEP is an obsolete wireless security scheme:

      https://en.wikipedia.org/wiki/Wired_Equivalent_Privacy

   Is there some actual problem which you are trying to solve?  Care to
share some useful information about it?

   If you're trying to find the MAC address which your (unspecified)
cable-TV ISP wants to know, then I'd expect to find it printed on the
label of your cable modem.

   Visit http://netgear.com/support , put in your model number, and look
for Documentation.  Get the User Manual (at least).  Read.  Look for
"Label" and/or "MAC address"?  Further reading might not hurt, either.