I am sorry about the delay. I thought I had added the ":" after the source SVM name but I tried it just now and I get the same error. It does not like the ":" and if you leave it off it asks for the volumes. The -SourceVolume parameter does not take wildcards either.
Another interesting thing. When you look at Get-Help for the command for the -source parameter it says:
-Source <String> Specifies the source endpoint of the SnapMirror relationship in the format: [cluster:]//vserver/volume. This format may change in the future. When specifying a source endpoint, you must use either the source location, or the source cluster, source vserver, and source volume.
If I look an an existing snapmirror SVMDR configuration I see this value:
I then tried the command using -Source and -Destination but I still get the same error. Now I am trying to track down how to refer to the source location and if it is even the same in this command as the value return in the Get-Snapmirror command.