A DVI-D connector on a GPU sends out a digital signal only, while a DVI-I connector can carry both an analog and digital signals. Digital signals are for LCD monitors (Flat panels) and an analog signal is for older displays such as a CRT monitor.
The DVI-D will fit into DVI-L GPUs. The ones that come with the monitor should work just fine. If you don't have one, just google DVI-D Cable
Hope this helps!