A DP++ port automatically senses whether a DP or HDMI or DVI monitor is connected and does the signal conversion automatically inside the PC, so all you'd need is a "passive" cable that just changes the connector ends.  You'd have to look at your video card to see if any of its DP are marked with two plus signs next to a P inside a  [IMAGE] Read here for more details about passive vs active connectors. I guess you could try one of those cables, as long as you can return it...      
Kicking myself a little I couldn't figure this out, but I have never really used display port before. I have a Dell Inspiron 5675 with an AMD RX570 graphics card. I am trying to set up a second monitor. I have a monitor connected to the lone HDMI port on the 570, and can't really find a manual or a breakdown of the other ports on the Dell 570 card. Other 570's have a DVI and three 1.4 display ports, I only see three 1.4 display ports on the Dell 570 (in addition to the one HDMI). The monitor I have, a Dell P2412Hb, has VGA and DVI video inputs. I have a billion extra cables, but I'm not sure if any of them are a display port to VGA or display port to DVI. Can I just grab a random one off Amazon, or are there any limitations on the Dell 570 I am not aware of? Thanks.
Adding a second monitor to a Dell Inspiron 5675 with an AMD RX570