You don't get a serial number.
You install the software via the Creative Cloud application, which verifies your license through your Adobe ID.
Hope this helps clarify!
Thank you for the reply but it does not solve my problem.
I am able to install CC on my destop but when I want to install Lightroom and Photoshop I can only install the trial version. If I want to install the license version I am asked for a serial number. I pressed the info icon (the i in the cercle) and I went on the adobe/license website but my ID is not recognized.
You may need to call Adobe Customer Support if there's a problem with your subscription.
You do not need a serial number when the Creative Cloud process is working correctly. It recognizes your subscription by the fact that you've logged-into the Creative Cloud application using the Adobe ID under which you purchased the subscription.
Did you try, in the Creative Cloud application, explicitly logging out and back in?