First, you need to distinguish between IP addresses: public and private. Cox will assign a public address to your DOCSIS or ONT. This address is how the rest of the Internet (public) "sees" and routes data to your DOCSIS or ONT. You can view this address by Internet-searching: my IP. The search engine will either display your public address or provide links to other websites.
This public IP has nothing to do with your router or private network...other than the Internet routing your requested data to your DOCSIS or ONT. Your DOCSIS or ONT will then transfer the data to your router via MAC or Layer-2. There is no network-routing between a DOCSIS or ONT and a personal router. No network-routing = no IP address.
If your router used to assign private IPv6 addresses to your devices, it should still be assigning IPv6 addresses to your devices. If you didn't replace your router, its settings should still be the same as before. Unless you replaced your router with a non-IPv6 capable router.