Manual:$wgSVGConverterPath

Details
By default, when invoking a SVG converter, MediaWiki simply passes a command line such as, leaving it up to the operating system to locate the executable.

If your chosen SVG converter ($wgSVGConverter) is not in the executable PATH, you should use this setting to specify the directory in which the SVG converter is located.

You will almost certainly need to set this variable on Windows systems.