You can connect the 20pin header to the internal usb 3.0 motherboard, then connect the USB type A female to the external USB 3.0 device.
This USB 3.0 pin header adapter can be plugged to a free USB 3.0 pin header male of your mainboard in order to expand your system internally by two USB 3.0-A ports.
Thus you can connect e.g. an USB memory stick or USB-LAN stick.
Since the USB 3.0-A interface is compatible to its forerunners USB 2.0 and USB 1.1, you can still use your existing USB devices.
CY Motherboard 19pin USB 3.0 Header 1 to 2 USB2.0 9Pin Female Extension HUB Connector Adapter Port Multilier
Description
Motherboard 19pin USB 3.0 Header 1 to 2 USB2.0 9Pin Female Extension HUB Connector Adapter Port Multilier
USB2.0 HUB chipset inside, and support 480Mbps speed.
Support DC 5v 500ma current for each port.
Desktop 19-Pin USB3.0 HUB to USB 2.0 9 pin Connector Adapter Port Multilier
It can extend your motherbord USB3.0 19pin connector to 2*USB2.0 9pin connectors.