What is my external IP address with router?

That’s the internal address, obviously. You can test it by simply typing that address into your browser’s address line, and the login window of your router’s admin interface will respond. For external address, just http one of the numerous websites, that gives you the externally visible information of your system. For example: What Is My IP Address? IP Address Tools and Details - WhatIsMyIP.com.
If you have questions or need any assistance troubleshooting, just visit: Router Help | Google Mesh Setup