I am not with Laminar Research; just a flight simmer.
X-Plane 10 and x-plane 11 are totally different packages. There is no upgrade from one package to the other. Like you I have the XP10 disc version and have purchased the XP11 version. There is a digital download version available through Laminar Research. To do this you need a good internet connection.
If you want the official package and prepared to support the developers ie Laminar Research, purchase from them.
Be aware that to run XP11 disc version you are still required to insert disc 1 into a DVD drive whereas with XP10 there was an option to purchase a USB key (dongle) to replace the necessity to insert the XP10 disc 1. This dongle allowed the full set of discs to be stored away from possible damage.
There is a hybrid package sold under the Steam banner. This package is developed by a 3rd party organisation taking a commercial advantage of the work carried out by Laminar Research. There is no commercial arrangement between both parties. With any updates Laminar Research makes the updates available asoon as it is released whereas there is a delay (how long???) with this other package. Support the official developers and their ongoing work.
The official version can be ordered via firstname.lastname@example.org