Apple Logic Pro /LogicExpress Discussion

When I went to download my 9.1 update, I was asked for my serial #.  I 
typed in the serial # that shows when I click on About Logic under the 
Logic > Preferences tab.  I got a message saying that that was not the 
correct Serial #.  I assume this is because this is the serial# for my 
Logic Pro 9 Upgrade.  They probably want my original Serial # which was 
many years ago.  How do I find out my original Serial #?