Have your tried following this: https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network Where did it go wrong for you?

Sonos has no way of knowing you're about to get a new network. So you could have put in the credentials of your new network into the systeem when the old network was up, or you could have set up the new network with your old credentials. Then the system would probably not even have noticed there was a new router. 

I had similar recently.  Just set up the new Modem/Router with my old SSID and Password.  Saves a ton of time reconnecting all your kit, be it Sonos or other devices.