Go here and input your HD 6XXX model. AMD Drivers and Support for Radeon, Radeon Pro, FirePro, APU, CPU, Ryzen, desktops, laptops .
AMD doesn't support the HD 6xxx series GPU cards anymore. It is considered to be Legacy (old and non-supported). The last AMD Supported driver is from 2015 (official) and 2016 (beta) from here: AMD Radeon™ HD 6850 Drivers & Support | AMD . All the HD 6xxxx models you input will have the same old AMD Driver.