how to click to know the position in sortable list

how to click to know the position in sortable list

i have the following code to get the change of position, I dont know how to make the list tell me the position of a specific element when i click it. 


please give some idea. 
  1. $( "#sortable" ).sortable(
  2. {
  3.                start:function(event, ui) {
  4.  startpos=( $(ui.item).prevAll().length );
  5.                },


  6.                stop:function(event, ui) {
  7.                        stoppos=($(ui.item).prevAll().length );
  8.                }
  9. });