$all_ids = get_posts( array(
'post_type' => 'product',
'numberposts' => -1,
'post_status' => 'publish',
'fields' => 'ids',
'tax_query' => array(
array(
'taxonomy' => 'pa_years', // Hover over "Configure terms" and look for taxonomy=pa_years in the link
'field' => 'slug',
'terms' => '2016', // Is the slug under "Configure terms"
'operator' => 'IN',
)
),
) );
/*foreach ( $all_ids as $id ) {
echo $id ."<br>";
}*/