Best Way to Limit Zip Code to 5 Characters Only When Country is USA in Woo Checkout

yes I insert the following into functions.php file in a CHIKD THEME PLEASE, OR YOU WILL LOSE IT ON UODATE AMD NOT EVEN REMEBRR ABOUT IT

add_action(‘woocommerce_after_checkout_validation’, ‘custom_validate_us_zipcode’, 10, 2);

function custom_validate_us_zipcode($fields, $errors) {
// Check if the billing country is set to the US
if (isset($fields[‘billing_country’]) && $fields[‘billing_country’] === ‘US’) {
$zipcode = $fields[‘billing_postcode’];

// Check if the zip code is 5 characters long
if (strlen($zipcode) !== 5 || !ctype_digit($zipcode)) {
$errors->add(‘validation’, __(‘Please enter a valid 5-digit US zip code.’, ‘woocommerce’));
}
}
}