The drivers for the AMD Radeon R9 200 series are still available at AMD’s website. For some reason people can find them here is a direct link to the driver page. If the drivers become hard to find in the future we will put them up. Windows 10 is as high as the drivers go.
Just download the Adrenalin Edition 18.9.3 package for your operating system, unfortunately the last update was in 2018.