How to get License Key for Internet Security which was subscribed through Activation code

I had purchased "Bitdefender Internet Security" from 3rd party Ecommerce website. I was provided only with the Activation key, which seems to be valid as i logged into the Bitdefender Central.

The issue is I already have a trial pack running in my old system and I need to enter the license key to register. How can i find the license key?

Thank you!