You can enter your e-mail address you used to get pro in this link.
http://www.limewire.com/english/cont...pro_lookup.jsp

You also might want to check your junk mail folder for the e-mail. It does sometimes take up to 24 hours or longer on weekends to receive the e-mail with the link to your personal pro page.

I would suggest bookmarking your personal pro page for easy access for your 6 months of free upgrades.