Vishnu's answer only works if you have direct CLI access. AMPCLI, you'll have to go into Enter Commands to run 'dmidecode'. The dmidecode rpm is already installed if you're on AMP 8.2.5.1 or newer.
Ultimately, the hardware serial isn't what is gauged for support, it's the license key. If you're on 8.2.6 or newer, you can do the following:
Login to the AMPCLI
Go into Enter Commands
$ license
This prints out your AMP license key which is easier to trace than the hardware serial.