Actually there is not much to be done, you'll have to get a temporary disk area to migrate these VMs to change your HD's Storage.
After copy all VM´s to temporary area you´ll dismapp all volumes from storage of VMware, and do rescan in VMware, after change HD´s Storage, map new Storage LUNs and rescan again to appear your New DataStore, format all new volumes and back all VMs to new space and add to inventory if necessary.
If you have Storage VMotion licensed you can use it to migrate, or converter.
Via cli i dont know what command can help, lets hope other people reply. 