Get category list in dropdown box  WP

step1 : Create new template and followinig copy past code
step2: assign your this template in page in wp-admin

<?php $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
                $args = array('paged' => $paged,'post_type' => 'your custom post name', 'posts_per_page' => 7,'order' => 'DESC' );?>
                       
                  <form action="#" method="POST" name="mycategory" id="mycategory">
                      <?php wp_dropdown_categories($args); ?>
                  </form>