Answer:

An Extended Version Upgrade Key 1.0 to 2.0 is a code that may be used to activate an Extended Edition copy of Foxhound that was originally purchased as Version 1.0, after it has been upgraded to Version 2.

In this case the Foxhound Activation page will appear automatically when you start Foxhound, and it will request an Extended Version Upgrade Key 1.0 to 2.0.

You can purchase an Extended Version Upgrade Key 1.0 to 2.0 here:

See also...
What are the differences among the different editions of Foxhound: Rental, Basic and Extended?
What are the differences among all the activation keys?