In Windows 10, the .NET Framework 3.5 is enabled by turning Windows features on and off in Programs and Features in Control Panel by default.
However, it may happen that it is a Windows problem or it can not be installed.
The offline installation method is a useful option.
Offline installation method is using the Windows installation CD, and the installation path of DISM is specified by CD.
Dism /online /enable-feature /featurename:NetFX3 /All /Source:G:\sources\sxs /LimitAccess
You just need to have a Windows CD to use it.