using an old cable modem router as wifi router only

> any way that i can use my old netgear to use as a wifi router only...
> [...]

   I know of none, unless you can find a way to create an Ethernet
WAN/Internet port on the C7000v2.

   It should be possible to configure a C7000v2 (or any other Cxxxx
model) as a wireless access point, but that's not a router.  For
useless-to-you details, see, for example:

      https://community.netgear.com/t5/x/x/m-p/1463500

That's written for a Netgear C6300-as-WAP, but the steps are about the
same for any other router (any make/model) which lacks a one-step WAP
option.  But that's not much use without a router.