As I said, I'm not a KDExpert
! In Gnome, when it opens with the Desktop: go to Computer > Places and on the right there's a panel where there's a list of places including USB, CD, etc - external devices and other partitions. Highlight the one you want and rightclick; one of the pop-up menu choices is Open as Administrator. I use this mainly to open other partitions and access their files, but it also allows me to open external devices.
I've used Gnome for years but I'm going to install Mint KDE, to start getting familiar with the KDE environment, so I'll soon find out if this works in KDE!