need my cable moden CM 400 PIN number it does not apper on the Modem.
PIN number for what? That is usually a Wi-Fi Protected Setup (WPS) thing. Which means wifi. The CM400 is a plain old fashioned modem. It doesn't do wifi. So it doesn't have a WPS PIN number.
Feed in your model number and check the documentation for your hardware.
You may have done this already. I can't tell from your message.
You have posted your message in the section of this community given over to Nighthawk WiFi Routers. (This is easily done, given Netgear's impenetrable community structure.)
You might get more help, and find earlier questions and answers about your hardware, in the appropriate section for your device. That's probably here:
