Step1: List all USB connected device
it will lists all the available USB devices, and also the adapter is listed such as below:
Since it it from Prolific Techonology, you can get the driver here.
for those user using SiLabs CP210X, you can get the driver here too.
NOTE: Mac OS High Sierra 10.13 introduces a new feature that requires user approval before loading new third-party kernel extensions.
Go to System Preferences – Security & Privacy and click Allow.