Type in the Microsoft Visual Studio Command Prompt: where svcutil.exe. On my machine it is in: C:\Program Files\Microsoft SDKs\Windows\v6.0A\bin\SvcUtil.exe
I don't think it is very important to find the location of Svcutil.exe.
You can use Visual Studio Command prompt to execute directly without its absolute path,
With latest version of windows (e.g. Windows 10, other servers), type/search for "Developers Command prompt.." It will pop up the relevant command prompt for the Visual Studio version.