Hi,
For some aircraft, before being able to see them in the selection window, you need to check the box "show aircraft from previous versions" (or similar sentence).
For your PC12, the installation does not seem to be complete. I do not owe this payware and with so little information, I can't help you much with that. Try if you can find an installation procedure among the unzipped files or on the internet, make sure your X-plane 11 copy is up to date and if you can't find any solution, you should rather contact the PC12 developers. This forum is mainly for X-plane default install.
All the best with that,
Guillaume