Are you using Windows 7 or XP by any chance? Your .NET Framework version appears to be way out of date. You have version 4.0, which is about 12 years old (it was released in 2010). WeMod requires version 4.5 minimum. And the latest version is 4.8.
Here you go, to update it: Microsoft .NET Framework 4.8 offline installer for Windows - Microsoft Support.
If there’s still an issue, the full troubleshooting is here: I can’t Install WeMod / "There was a error installing the application" - #2 by Ravenfyre. 