Excluding categories-I can’t figure this out.

I am using this template: https://www.ideasfloataway.com/blog/

And I am trying to get it so that the sidebar only posts links for category 3. I’ve looked online, and at the tutorials but I cannot figure out how to do this. The sidebar.php file looks like this:

<div class="leftColumn">
		<?php if ( !function_exists('dynamic_sidebar')
        || !dynamic_sidebar() ) : ?>

						 <h2><span>My</span>Scripts</h2>

<?php

$today = current_time('mysql', 1);

if ( $recentposts = $wpdb->get_results("SELECT ID, post_title FROM $wpdb->posts WHERE post_status = 'publish' AND post_date_gmt < '$today' ORDER BY post_date DESC LIMIT 10")):

?>

<ul>
<?php

foreach ($recentposts as $post) {

if ($post->post_title == '')

$post->post_title = sprintf(__('Post #%s'), $post->ID);

echo "
<li><a>ID)."'>";

the_title();

echo '</a></li>
';

}

?>

</ul>
<?php endif; ?>			

<?php endif; ?>
</div>

Can someone please help? Thanks.