Get form values in hook_user_insert()
The $account argument have the data that you like, but the password is protected.

It's not the best practice, but you can use reflection to get it:

/** @var \Drupal\Core\Field\FieldItemList $passObject */
$passObject = $account-&gt;get('pass');
/** @var \Drupal\Core\Field\Plugin\Field\FieldType\PasswordItem $passItem */
$passItem = $passObject-&gt;get(0);
$reflection = new \ReflectionClass($passItem);
$reflectionProperty = $reflection-&gt;getProperty('values');
// This do the magic.
$reflectionProperty-&gt;setAccessible(true);
$pass = $reflectionProperty-&gt;getValue($passItem)['value'];


See more about hook_user_insert here.