change string – pdf invoice change to “receipt”

I would like to change invoice to “receipt” I tried it with a function but it didn’t work. Can you take a look at it?

add_filter( ‘wpo_wcpdf_filename’, ‘wpo_wcpdf_custom_filename’, 10, 4 );
function wpo_wcpdf_custom_filename( $filename, $template_type, $order_ids, $context ) {
    $invoice_string = _n( ‘invoice’, ‘invoices’, count($order_ids), ‘woocommerce-pdf-invoices-packing-slips’ );
    $new_prefix = _n( ‘receipt’, ‘receipts’, count($order_ids), ‘woocommerce-pdf-invoices-packing-slips’ );
    $new_filename = str_replace($invoice_string, $new_prefix, $filename);

    return $new_filename;
}