Modem Router IP Address

I recently received a new router and was able to get my televisions and Amazon Alexa devices to connect to it.

I am now trying to reconnect my 5 wi-fi extenders to the new router but cannot find the login page on my PC to access the router. I have tried 192.168.188.1 and 192.168.10.1 among several others.

The closest I could get was using the IP 10.0.0.1. It gives me the page to login to my router, but it will not accept the user name and password of admin.

I tried using the name of my new Network and entered the correct password, but a pop-up shows either the user name or password are incorrect.

What IP address do I enter into my browser to access the router so I can get my extenders to connect?