IF the customer had the V3 proxy in place already:
You will need to know how to see the fields in the proxy community string and change them to match what we need for the native SNMPv3:
You will replace the community string field with:
&v3(UserName:"username", AuthType : MD5, AuthPass : "authpass", PrivType : DES, PrivPass : "privpass")
AuthType can be MD5 or SHA
PrivType can be DES or AES
The IP address inside the proxy community string should be moved to the leftmost column and replace the 127.0.0.1 IP address that is used to talk to the proxy.