Welcome to BBR.
According to the manual the unit connects a single PC to the Cable network. Assuming your ISP only provides a single IP address to residential customers, typical for residential accounts, in order to connect multiple devices you need a broadband router.
»techhelpportal.com/docs/DHG535.p ··· G535.pdf
The Netopia 3346N is a ADSL2 broadband router, as such the WAN interface is DSL. Since you now have Cable you need to get a router that has an Ethernet WAN port to share your cable connection.