Hi raizaduran. You can do this by modifying two theme files:
1. Copy archive.php and search.php to a child theme. If you’re not running a child theme you can create one using the process described on the theme web site:
https://docs.presscustomizr.com/article/239-using-a-child-theme-with-hueman
2. Locate this section of code in both files:
<div class="post-list group">
<?php $i = 1; echo '<div class="post-row">'; while ( have_posts() ): the_post(); ?>
<?php get_template_part('content'); ?>
<?php if($i % 2 == 0) { echo '</div><div class="post-row">'; } $i++; endwhile; echo '</div>'; ?>
</div><!--/.post-list-->
3. Change this:
if($i % 2 == 0)
to this:
if($i % 3 == 0)
4. Add this CSS to your child theme style.css file:
/* set post width for 3 columns */
.archive .post-row .post, .search-results .post-row .post {
width: 33%;
}