Hello, i'm pretty sure your PC does have a PCI-EXPRESS slot because this is a newer line and basically everything made after 2007 has one. But the best way to be sure is to open up the case and look for yourself. A PCI-EXPRESS slot will have a slot like this
The bottom Black one is a PCI-Express slot. and that Notch :
the | will be closest to the back wall of your case.
Also if getting a big GPU like that I recommend Getting a 500-600Watt PSU to run safely.