Change SKU Text

function translate_woocommerce($translation, $text, $domain) {
    if ($domain == 'woocommerce') {
        switch ($text) {
            case 'SKU':
                $translation = 'Part No';
                break;
            case 'SKU:':
                $translation = 'Part No:';
                break;
        }
    }
    return $translation;
}

add_filter('gettext', 'translate_woocommerce', 10, 3);