Show pop up message for specific categoryies

1) Open your templates/content-product_cat.php file.

2) Locate the following piece of code:

<li <?php wc_product_cat_class(); ?>>
<?php do_action( 'woocommerce_before_subcategory', $category ); ?>

<a href="https://wordpress.stackexchange.com/questions/204313/<?php echo get_term_link( $category->slug,"product_cat' ); ?>">

3) Replace the line

<a href="https://wordpress.stackexchange.com/questions/204313/<?php echo get_term_link( $category->slug,"product_cat' ); ?>">

for the following piece of code:

<?php if ($category->name == "adults1" || $category->name == "adults2") { ?>

    <a onclick="return confirm('The content you are about to view are of a mature matter. Please be advised that the content may not be suitable for those under the age of 18')" href="https://wordpress.stackexchange.com/questions/204313/<?php echo get_term_link( $category->slug,"product_cat' ); ?>">

<?php } else { ?>

    <a href="https://wordpress.stackexchange.com/questions/204313/<?php echo get_term_link( $category->slug,"product_cat' ); ?>"> 

<?php } ?>

4) Replace "adults1" and "adults2" for the names of the two categories you want to control.

Hope it solves your issue.