how to get the index number of my Tumblr posts when in Infinite Scroll

how to get the index number of my Tumblr posts when in Infinite Scroll

basically, I want to display the number my Tumblr posts. I have made
different attempts but each time the index numbering starts again from 0
after the new content is loaded. How can I make the number a continuation
from the previously loaded posts.
$('#content').infinitescroll({ binder: $(window), debug: true,
itemSelector : ".post", navSelector : "#pagination", nextSelector :
"#next-page" },function(arrayOfNewElems){
... H.E.L.P
});