How do I change the password and ID in my cox router

ARRIS MODEL TM3402A  PN TMO2DAF3402  TKS

This isn't a router.  It's a DOCSIS-VOIP modem.  Did you want to change the password to what's connected to this device?

Hi Bruce, I meant a modem... I'm having a hacker and watched some you tube and they suggest several things, including changing your password and ID in the modem. What do you think?

I have this modem but I've never seen an option to change any credentials.  You can try to find an option by typing into an address bar:  192.168.100.1

If it's not wireless, hackers can't access it without being directly wired to it.  Do you have a wireless router attached to the modem?

How do you know you have a hacker?