I have started building the mini Hawk although the designation for the wiring is quite clear on the module there is no pin out for the actual switch. The other problem there is no details for the usb extension board (see attatched), I would assume the two plugs go into the i2c board however i thought it best to check first.
Unfortunately the Mini Pixhawk does not have the abiity to use an external USB module like the one in your image. That is actualy a two in one USB/External LED module but with the mini unmanned hawk kit you only need to use the external LED connected to the I2C hub as shown in the image below.
If you want to use an external USB my suggestion would be to purchase a micro USB extension cable and just use that on your drone.
Hope that helps