What you need to know is that a "PC Card slot" (notice the capitalisation: "PC Card" is a single term) is the common name for a "PCMCIA card slot". PCMCIA (Personal Computer Memory Card International Association) is a standard originally developed for adding memory to laptop computers, but it soon expanded to all sorts of network applications (modem, ISDN, Ethernet, wireless LAN, etc.). It is now a de facto standard for adding network and data storage functionality to laptop computers.

In Dutch, the proper name is more prevelant than the common name, i.e. "PCMCIA slot" rather than "PC Card slot". And, in turn, "slot" is AFAIK more common than "sleuf", although that's a choice that's for a native speaker to decide.

Je vertaling wordt dus: "drie USB-poorten, twee PCMCIA slots, ..."