Get user by meta data key and velue

This how my stored data function is for this meta group and get data

stored

$certification = array(
        'course_id' => $certificate_id,
        'course' => $certificate,
        'date' => $date,
        'instructor' => $certifying_instructor,
        'school' => $school,
        'last_update' => date('d-m-Y'),
    );

    add_user_meta( $user_ids, 'certifications',  $certification );

and this get data

$users_detail = get_user_meta($user_id);
$certificates = $users_detail['certifications'];

$n_course_id = array();

foreach ($certificates as $value) {
   $course = unserialize($value);
   $course_id = $course['course_id'];

   foreach ($course_id as $courses) {
     array_push($n_course_id, $courses);
   }

}

by this function i can get all list but i want to get only one of them