Orderby Google Analytics. Meta_key?

Hello,

My Goal is to sort my posts by pageviews or other values using Google Analytics. So my code would look like this:

$query = array(
     'posts_per_page' => (int) $count,
     'post_type' => 'post',
     'meta_key' => ???,
     'orderby' => 'meta_value_num',
     'tax_query' => array(
		array(
			'taxonomy' => 'category',
			'field'    => 'name',
			'terms'    => $cato2,
		),
	),
);

My Problem is that I don’t know which value to put in ‘meta_key’. I already studied the Google Analytics API but I’m still desperate.