Building a View or Panel(?) from an existing node and customize path and breadcrumb
The base url of the view would be home/resources/gallery/%/%/% this would ensure that the view is invoked only when all three arguments are present. 

and Rather than sending one argument to the view you would be seinding three arguments. 


Conference Type - The taxonomy term
Continent - The Taxonomy term
conference-name


Since your content would have all three condition to be true you would get the required url. Other wise you can set it to show a page not found or may do some other things as you want.