The purchase confirmation code is available in the licence certificate which you received once you made your purchase from Envato marketplaces.
This licence certificate can be found in two places:
The first one is via a link in the email you received from Envato after your purchase.
The second one is in your Envato account, in the "Downloads" tab, and beside each item you have purchased there will be a "Licence Certificate" link. Click this link and inside the plain text file you will see your code entitled "Item Purchase Code".