Upgrading for a Friend from 6.0

I have a friend who was running software under Windows on his Mac using Parallels 6 he bought in 2010. He has an old email with the confirmation of the purchase from Parallels and the disk image file:

ParallelsDesktop-parallels-en_US-6.0.11822.604190​

The email does not include a license code or number but does say:

Congratulations on the new purchase from the Parallels Online Store.
Order number: 6959951216
Received: September 21, 2010
The following email is a summary of your order. This email serves as your proof of purchase. If you paid by credit card, this charge will appear as DRI*Parallels, Inc. on your credit card billing statement.​

He wants me to upgrade this to the latest Parallels 15. How do I do this? The password provided to him in the email 10 years ago does not work on your site and you've probably changed the way this works in the last 9 years.

I have already installed software using an evaluation copy of Parallels 15 so ideally I'd prefer to use a license key rather than have to install 6.0 and then upgrade to 15 if that still works.

 

No one from parallels here?

 

Hi, could you also provide us with your friend's email address, which has been used for Parallels Desktop 6 registration?
And if we find a previous key you will be able to purchase and activate Parallels Desktop 15 with the upgrade key.

 

Sure, I can do that. How can I send it to you without posting it publicly here. He'd probably not like that.

 

Please reply on mine private message with the requested info.