The error message says you have installed the .NET Core RUNTIME but not the DESKTOP RUNTIME package.

Try these links:
dotnet.microsoft.com/download/dotnet-core/thank-you/runtime-desktop-3.1.5-windows-x64-installer
dotnet.microsoft.com/download/dotnet-core/thank-you/runtime-desktop-3.1.5-windows-x86-installer
Or if they fail to install because of Windows 7 try these older ones:
dotnet.microsoft.com/download/dotnet-core/thank-you/runtime-desktop-3.1.0-windows-x64-installer
dotnet.microsoft.com/download/dotnet-core/thank-you/runtime-desktop-3.1.0-windows-x86-installer

However keep in mind that we do not support Windows 7 anymore. So if this does not fix your problem please consider upgrading your Windows especially as you also no longer receive security updates for it (Microsoft dropped support as well).