Hi,
Sorry for the late reply.
The file is just a random set of folders with worldwide random placemarks.
Such a file is not suitable for GPX unless you want all the placemarks to be converted to gpx:wpt (waypoints).
There is no track nor route in your file.
So all in all it doesn't make sense to convert your My Places.kml file to a GPX file.
As is written in the renewed Gui (also zip file is updated) for a good transformation the KML file should have the structure of Waypoints folder, track folder with subfolders for tracks and a similar structure for routes.
Cybarber