If you have your installation media connected, you can sometimes use the Windows interface.
The ISO method is the safest and most reliable for 64-bit systems. Net Framework 3.5 Offline Installer Windows 10 64 Bit
dism /online /enable-feature /featurename:NetFx3 /all If you have your installation media connected, you
Download your offline source from a trusted Windows 10 ISO, then run DISM. Never use "activator" tools or repacked EXEs. Net Framework 3.5 Offline Installer Windows 10 64 Bit