/Provider=ProviderNameOrId /Type=ShadowType - Displays all volumes which may be shadow copied using the provider specified ...

%1 %2 [/Provider=ProviderNameOrId] [/Type=ShadowType]
    - Displays all volumes which may be shadow copied using the provider 
    specified by ProviderNameOrId.  If ShadowType is given, then lists only 
    those volumes that may have a shadow copy of that type.
    - The Provider ID can be obtained using the List Providers command.
    When entering a Provider ID, it must be in the following format:
       {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} 
    where the X's are hexadecimal characters.

    Example Usage: vssadmin List Volumes 
                            /Provider={b5946137-7b9f-4925-af80-51abd60b20d5}
                            /Type=ClientAccessible
    - Valid shadow copy types: