Fetch Active Install Count from WordPress Plugins API

functions.php

<?php
function get_plugin_install_count( $plugin ) {
	$api = plugins_api( 'plugin_information', array(
		'slug' => 'popup-maker',
		'fields' => array( 'active_installs' => true )
	) );
	
	if( ! is_wp_error( $api ) ) {
		return $api->active_installs;
	}
}