WP_Query Order Posts by Advanced Custom Field.

$args = array(
  'post_type' => 'xxx',
  'order'     => 'ASC',
  'meta_key'  => 'custom_field_name',
  'orderby'   => 'meta_value'
);

$query = new WP_Query($args);

if($query->have_posts()){
  while($query->have_posts()){ $query->the_post();

  }
}