WordPress AJAX load post metadata in modal

I have a custom page template (front-page.php) and I have a custom metabox which is assigned to this page template.

Metabox have 7 sections, and each section have 2 inputs. It looks like:
1. Client logo image url (input)
2. Client details (textarea)

At frontend showing 7 client logos via:

<?php echo get_post_meta($post->ID, 'client_logo', true); ?>

What I need to do is to AJAX load client details post meta in the modal box when you click on the clients logo.

If you click on client 1 logo you see client 1 details, if on client 2 logo you see details post meta for client 2, etc etc

I have some code but I have no idea how to use it. Maybe someone have a solution for this?

( function( $ ) {
// AJAX loading client information
    var page = 1;
    var loading = true;
    var load_posts = function(){
            $.ajax({
                type       : "GET",
                data       : {'What should be here?'},
                dataType   : "html",
                url        : "link to php file which is return data? what should be at the php file?",
                success    : function(data){
                    } else {
                    }
                },
                error     : function(jqXHR, textStatus, errorThrown) {
                    alert(jqXHR + " :: " + textStatus + " :: " + errorThrown);
                }
        });
    }

    // Load more posts on click
    $('a.popup').click(function() {
      loading = true;
      load_posts();
      return false;
    });
    load_posts();
} )( jQuery );