Display Custom Fields Meta Box on Category, Tags and CPT

if You want to get all tag/category of custom post types then use the below code.

$terms = get_terms([
    'taxonomy' => 'testimonial_tag', // here you can add you custom taxonomy name
    'hide_empty' => false,
]); 
$result =  new WP_Query($terms);

If you want to get a particular custom field value from a particular taxonomy/tag then use below code

    echo get_field('tes', 'testimonial_tag_18');
eg : get_field('custom-field-name', $term->taxonomy . '_' . $term->term_id);