There is an easy way to find the LUN number at least to match it up to what your SAN provided.
From the command line, just type: vxdisk list
This command should list all the harddisks and the PCTL information. (Port / Channel / Target / LUN)
Or you can simply go to VEA and click on "Disks" on the left tree pane and then scroll to the right on the right side to see the PCTL information.