Hi,
I think the CmdLet you are looking for is "Get-NcSnapmirrorDestination". Also you can use "Invoke-NcSsh" for any command line operation that does not have a corresponding PowerShell CmdLet. You might also consider querying the OCUM database for this information. Here is an example using powershell (modify the sql query to meet your requirements)
http://community.netapp.com/t5/Developer-Network-Articles-and-Resources/Query-OCUM6-Database-using-PowerShell/ta-p/98184
Hope that helps.
/matt
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