Just to make sure are you looking for the modem Wi-Fi password or the modem GUI or web manager login credentials?

If you are looking for modem default Wi-Fi name and password you can check on the label it will be mentioned as SSID and below that password. If that is not seen on the device that you are trying to connect then you can check for the credentials on the modem GUI or the web manager page if you are unable to access GUI then need to reset modem for 15-30secs. After resetting the modem will go to default setup any custom settings will be removed so use the default network name and password to connect to your network.

http://arris.force.com/consumers/articles/General_FAQs/SVG2482AC-Wi-Fi-Password-Retrieval

http://arris.force.com/consumers/articles/General_FAQs/SVG2482AC-First-Time-Installation