Add-on development: How do I validate an additional pin field on my wordpress login form page?

I was able to add an additional field to my wordpress login form using the following code in the wp_login.php file, tap stackxchange

add_action (& # 39; login_form & # 39 ;, & # 39; my_added_login_field & # 39;);
my_added_login_field () {function
// Produce your HTML
?>

Pin

I need help to validate / connect the new custom field to a column of data in wp_users, called serial. I want users to be able to log in if their username, password and new serial number of the database is correct / exists.