welcome to communities. !!
I am assuming you are using cluster mode ontap 8.3.+
lun show command would show you Serial Number which is in Hex - which would match the NA ID from vsphere
"lun show -vserver <vserver name> -path /vol/<volumename>/<lunname>"
scroll down till you see "Serial Number (Hex) : xxxxxxxxxxxxxxxxxxxxxx "
this xxxxxxxxxxxxxxx whould be matching the NA ID from vsphere.