Use c7000 as AP connected to my cn1000 cable modem

> Use c7000 as AP [...]

   That should be possible.

> [...] connected to my cn1000 cable modem

   Why?  That would appear to be approximately pointless.

> What settings would I have to change so I can use the c7000 as ap and it
> should handle DHCP as it looks like the cm1000 does not support this.

   A CMxxxx is a modem, not a router, so it will not serve as a DHCP
server.

   A Cxxxx is a modem+router, but it has no Ethernet WAN/Internet port,
so it can't be used as a router with a CMxxxx modem.

   If a Cxxxx is configured as a wireless access point, then that
configuration would disable its DHCP server.

   You appear to want to use your C7000 as a router with an Ethernet
WAN/Internet port.  It doesn't have one, so you can't do that.  Although
configuring the C7000 as a WAP may be possible, if you do that, then it
still won't be a router.

   Possibly interesting, but only if you get a router:

      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 you apparently want a router, not a WAP.