When you purchase the usb to ethernet adapter it should come with the appropriate drivers.
Do you have administrative rights to your router? You may need to obtain some information from the router via its administrative pages.
Try to purchase the USB to ethernet adapter that is the same brand name as your router and with matching ethernet standards.
Disable the wireless adapter on the laptop and then install the ethernet adapter following the User Guide/Manual instructions.
Take your time, be careful to type accurately, and write down what you do. Note any error messages.
You will be configuring the adapter so your laptop can join your network via the network name, password, etc.. Have that information ready.