The NAS does not have a USB host mode for direct USB PC access
(i.e. no USB direct connection possible) You must use Ethernet.

Solution:

You need:

A normal Ethernet cable (RJ45)
No crossover necessary, the NAS supports Auto-MDIX.

PC with LAN port (or USB Ethernet adapter)

Establish the connection:
Step 1: Cabling

Connect NAS → PC via Ethernet.

Step 2: Set static IP addresses

As there is no DHCP server, both devices must be assigned fixed IP addresses.

On the QNAP:

On the NAS display: Main Menu → Network → select the port

Set IP manually, for example:

IP: 169.254.100.10

Mask: 255.255.0.0

Leave gateway empty

(If QTS is already running, you can also set it via HDMI/Keyboard: Control Panel → Network & Virtual Switch)

On the PC (Windows):

Control Panel → Network Adapter → Properties

Select Internet Protocol Version 4 (TCP/IPv4)

Use the following IP:

IP: 169.254.100.20

Mask: 255.255.0.0

Gateway empty

Or simply connect both devices to the router ;-)