Plugable includes two different USB cables in the box with the UD-3900Z that can be used to connect the dock to your laptop.

One USB 3.0 Type-A cable to connect laptops with USB Type-A ports, and one USB 3.0 Type-C cable to connect laptops with USB Type-C ports. Only one cable is necessary, and we include both cable types to enable connecting the UD-3900Z to laptops with different port configurations. 

If the included three foot long USB 3.0 cables are not long enough, longer cables up to six feet in length can be purchased separately. We don't recommend cables longer than six feet due to potential performance issues. 

An example of a six-foot USB-A cable can be found here: LINK 

An example of a six-foot USB-C cable can be found here: LINK