3PAR-wise, it's in Provisioning --> VLUNS --> Active VLUNs and is called "Virtual Volume WWN". The last four digits are the last four digits of the 3PAR Serial Number (at least on our V400). There is another WWN-column ("WWN/iSCSI Name") which is something completely different, don't mix them up!
With the CLI, you can see the WWN with
Code:
showvv -d <vvname>
On ESX, it's part of the the naa.<WWN>:1 - string.
On creating vvs with a common WWNs per CLI, you have two options as well:
1) Create primary and secondary on your own and change the secondarie's wwn per
Code:
setvv -wwn <wwn>
2) Create just the primary volume, create the remote copy group, and make rcopy create the secondary with the
Code:
admitrcopyvv -createvv
command.