Problems with Wordpress Loop

Question

I’m creating the page Category.php and using a Custom Post Type called Father. Within that post type has some categories: 1, 2, 3, 4 etc. What I wanted was to enter the page category 4, showed only the posts of this category, but is showing all the posts that Post Type.

The loop that I’m using is this:

$args = array(
    'post_type' => 'pai',
); 

$loop = new WP_Query($args);
if ( $loop->have_posts() ) : while ( $loop->have_posts() ) : $loop->the_post();

<p>Existe Posts</p>

endwhile;

else:

<p>Não Existe Posts...</p>

endif;
wp_reset_postdata();