Licensing issue: how to get the license key to enter at the upgrade store

Good morning, I have a Family Mac license currently and had to add a PC to our household. I clicked on the link to see what my price would be to upgrade to the Mac+Family Bundle but it requests a license number. I requested the license number via email. I received the email and I can't seem to do anything with the links, the download or see the license to enter it into the tool.
I searched through my iPhone to see if I could copy the license from there over to the tool, but I don't see a license number there either. I'm probably missing something basic, but any help you could provide so that we can see the upgrade price. I'd love not to have to drop $50 on top of what I've already purchased. Thanks for any help!
-Shana