What you’re wanting to do in most situations is to actually locate the command you’re using. So, since you’re using ImageMagick’s command ‘convert’ you’d actually search for that:
This will give you the path from which you’ll be running the ImageMagick command. So, for example:
So, whereis, is the right way to go about locating ImageMagick, but if you’re looking the path to the ImageMagick commmand you’ll be using, than that, is what you’ll need to search for.