if your theme not changed or its like classic windows you need to install uxtheme patcher from here and after restart select new theme from personalization. Note: Please unistall old or other version of skin packs before install new one.
On Win10 to remove 3D Objects folder, OneDrive and Quick access from This PC and Navigation Pane use Winaero Tweaker from here To have skinned taskbar and start menu on Windows 10 you need to install Start is back from here Best work on 100% scale and layout size, you need to set it from display setting, also for remove Windows Ribbons install Old New Explorer from here.