When you purchased the pro version, LW sent you a personal download page link. If you're still within the 6 months update limit, you can go to this page and download the update from there.
If you have passed this time limit, you might go to the official LW website and purchase an extension (if possible) for areduced amount, or repurchase. Using the free basic version is, of course, also an option:
http://www.limewire.com/