Add prefix to url, but products not showing in page SHOP

I use the following code to add the prefix:

add_action('init','change__permalinks');
function change_permalinks() {
 global $wp_rewrite;
 $prefix = 'us';
 $wp_rewrite -> use_trailing_slashes = false;
 $wp_rewrite -> $prefix . $wp_rewrite -> page_structure.'/%pagename%';
 $wp_rewrite->flush_rules();
}