Require a duplcated B2 extensi

Hi there,

My mom came to visit us year of 2000 and we applied for a stay extension for her. However, we have not received the decision from the INS. But the status of the application from the INS online states that the notice was returned by USPS because they could not deliver to our new address (we moved about 6 months after filing the application). Does anyone know how to file an application to the USCIS to ask for a copy of the notice? What form should we file?

Thank you very much!