Nighthawk C7000 compatible with fios?

> [...] Is there a way to change some setting(s) so I can continue using
> this router/modem, but only as a router with fios? [...]

   Assuming that your "fios" is Verizon Fios, and that that service
provides an Ethernet connection, then sure, _if_ you can "change some
setting(s)" and get your C7000 to sprout a WAN/Internet Ethernet port.
Otherwise, you're out of luck.

   Netgear Cxxxx models lack WAN/Internet Ethernet ports, which makes
them almost useless for other purposes.  About the only way to repurpose
a Cxxxx is as a wireless access point, not as a full-function router.