In many cases, plugging the adapter in and running Windows Update (Settings > Update & Security > Windows Update > View optional updates > Driver updates) will fetch the driver automatically.
Unlike a standard USB mouse or keyboard, a USB-to-Serial adapter requires a specific driver to translate USB packets into RS-232 serial signals. Without the correct driver, your operating system will see the device as an "Unknown Device" or simply ignore it. digitus usb 2.0 serial adapter driver download