I want to use a new ethernet cable i bought but the ethernet controller drivers aren't installed and I don't know how to find them. Can someone help me figure out where to find these drivers and fix this issue.
The drivers should be available on the motherboard manufacturer's website for your motherboard in the downloads section.
I've done this and ran the setup but now it has replaced the ethernet controller with something called and 'Unknown device' that says it needs some drivers to be installed, but once again I don't know what they are
Without listing your exact specs, no way to know what you need to install. Did you make sure you downloaded the correct drivers for your computer/motherboard model?