Custom Taxonomy / Sub Categories

Hi,

I added custom taxonomies to my custom post type.

I know want to display the taxonomies, which I can do with the code below.
But, I have parent categories and child categories.
How do i display only the child categories of a certain parent category?

Thank you.

<?php
            $term = get_field('tour_category' );
if( $term ) {
  foreach($term as $t) {
    $t = get_category($t);
    echo $t->name;
  }
}
?>

https://www.ads-software.com/plugins/advanced-custom-fields/