I am displaying numbers (non currency) via an advance custom field of paid_attendance - however by default number fields in ACF do not include commas or decimals etc.

I would like for commas to be included when the numbers from paid_attendance are output to the user on the front end. I am aware this can be done through the template file but I need to make it global via functions.php. I am probably way off, but below is the code I put together. Any help would be greatly appreciated.

// Return number with commas
function fix_number( $wpdb ) {
$number = get_field('paid_attendance');
number_format($number)."<br>";
}
add_action('fix_number');

I am displaying numbers (non currency) via an advance custom field of paid_attendance - however by default number fields in ACF do not include commas or decimals etc.

I would like for commas to be included when the numbers from paid_attendance are output to the user on the front end. I am aware this can be done through the template file but I need to make it global via functions.php. I am probably way off, but below is the code I put together. Any help would be greatly appreciated.

// Return number with commas
function fix_number( $wpdb ) {
$number = get_field('paid_attendance');
number_format($number)."<br>";
}
add_action('fix_number');

EDIT Below is the fix and I have now got it working. Clearly and as Rick mentioned I was not using hooks properly. After reading deeper into the ACF docs and consulting other users on their forum, I was able to do what I need.

add_filter('acf/format_value/name=paid_attendance', 'fix_number', 20, 3);
function fix_number($value, $post_id, $field) {
  $value = number_format($value);
  return $value;
}