you need the WP_Query Before your Code:
<?php
$allCat = array(
'posts_per_page' => 3,
'tax_query' => array(
array(
'taxonomy' => 'category-products',
'field' => 'slug',
'terms' => 'your-slug',
)
)
);
?>
<?php $all_product = new WP_Query($allCat); ?>
<?php if($all_product -> have_posts()) : ?>
<?php while($all_product -> have_posts()) :
$all_product -> the_post(); ?>
<li><a href="https://wordpress.stackexchange.com/questions/163683/<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
<?php endwhile; ?>
<?php endif; ?>