atkp-product & shop_id

// WP_Query arguments
$args = array(
	'post_type'              => array( 'atkp_product' ),
	'meta_query'             => array(
		'relation' => 'AND',
		array(
			'key'     => 'atkp_product_shopid',
			'value'   => '58',
			'compare' => '=',
			'type'    => 'CHAR',
		),
	),
);

// The Query
$query = new WP_Query( $args );