Thanks for reaching out and sorry for the delayed response.
If you're talking about the Google Home app, you don't need to change the Wi-Fi on it since it will depend on the connection of your phone. If you're referring to your Google Home or Google Nest speakers, you can use the steps below.
If both the existing and the new Wi-Fi networks are available.
If the original Wi-Fi network is no longer available or accessible.
Let us know how it goes.