jquery plugin won’t fire when hamburger class element clicked

This should work for you.
I just copied your code and made adjustments.

jQuery.noConflict();
jQuery("li.menu-item-47 a").on("click",function( event ) {
 event.preventDefault();
 if(confirm("YOU ARE LEAVING THE WEBSITE" + '\n' + "" + '\n' + "You are being connected to a secure bill payment system.  Press Ok to continue.")) {

  window.open( this ,'_blank'); //This will open the website in a new tab
 }
});