you can easily determine what you want using vSphere client or run few commands at the console
all VMs are located under /vmfs/volumes/your_datastore/
to look for all vmdk related to a VM, you can read the config from each VM vmx file located under /vmfs/volumes/your_datastore/your_vm/your_vm.vmx
At the unsupported console, type the following
cat /vmfs/volumes/your_datastore/your_vm/your_vm.vmx | grep -i filename
you will get the output showing all vmdk for that particular VM similar to below
scsi0:0.fileName = "winxp.vmdk"
take note, if you have snapshots, your vmx will point to the latest snapshot
scsi0:0.fileName = "winxp-00001.vmdk"
also note, this .vmdk is only the disc descriptor file and normally its very small & byte in size, it describes which flat/delta vmdk file to use, this is the actual data for your VM
so if you look at the content of the disc descriptor file
cat winxp-00001.vmdk
you will get output similar to
parentFileNameHint="winxp.vmdk"
RW XXXXXXXX VMFSSPARSE "winxp-00001-delta.vmdk"
Just a brief intro on vmdk file, it can get confusing but really good to know when you have problem with snapshots and never manually edit the vmx file to point to the base vmdk when you have snapshots, if you start the VM and the file is modified, all snapshots can become useless