This appears to be very old, but I happened to run into this issue - and find the answer - this evening. The help file means exactly what it says:
vmrun clone "Path to vmx file" "Path to destination vmx file" full|linked [-snapshot=Snapshot Name] [-cloneName=Name]
Like me on my initial attempt, you appear to be only specifying the paths rather than the vmx files.
Try this:
vmrun -T ws clone \path\sourcefile.vmx \path\targetfile.vmx full -cloneName=NameOfTheClonedVM
Updated to add the 'clone' directive in the syntax. Note that for this to work, the VM must be powered-down or the optional snapshot directive must be specified and pointed at a snap of the VM in a powered-down state. With the snapshot directive, it would look something like this:
vmrun -T ws clone \path\sourcefile.vmx \path\targetfile.vmx full -snapshot=snapshot2clone -cloneName=NameOfTheClonedVM