Where can I connect this USB 3.0 cord?
I'm afraid you can't use that cord.
If you look at the specifications for your board, you'll see all the USB ports it supports:
ASMedia® USB 3.0 controller :
2 x USB 3.0 port(s) (2 at back panel, blue)Intel® Z68 chipset :
12 x USB 2.0 port(s) (4 at back panel, black, 8 at mid-board)
There are only two USB 3.0 ports (the blue ones at the back), and the other 12 (black) are USB 2.0.
That board seems to be something of a "value" board because a space for the connector in question does exist, but is not actually implemented. You can see where it should be on your board in the highlighted area in figure 1 and where it is implemented on a similar, but "deluxe" version of your motherboard in the highlighted area in figure 2 (the photos are scaled down; open them in a new tab to see them full-size).
You have two other options:
Get an extension cable and plug it into the blue port(s) at the back. They can be had on eBay for a couple of dollars.
Try to find a USB 3.0 male header to female plug adapter. Unfortunately, most adapters tend to be female on the header end, or male on the plug end.
Figure 1: ASUS P8Z68-V LX
Figure 2: ASUS P8Z68-V PRO
If you want to use the header on your case, you'll have to buy an expansion card to connect it. Silverstone makes one that's currently ~$23 on Amazon. You'd plug your cases table into the black header and a 4 pin Molex power connector from your PSU into the white one.
