We’ll use same code as shown in this post to find all posts with a specific custom field value.
That is same as getting ACF values from custom post type.
This following example has complete code with WP_Query too.
<?php
// args
$args = array(
'numberposts' => -1,
'post_type' => 'guest_posts',
'meta_key' => 'blog',
'meta_value' => 'yogeshchauhan'
);
// query
$the_query = new WP_Query( $args );
?>
<?php if( $the_query->have_posts() ): ?>
<ul>
<?php while( $the_query->have_posts() ) : $the_query->the_post(); ?>
<li>
<a href="<?php the_permalink(); ?>">
<img src="<?php the_field('img_thumbnail'); ?>" />
<?php the_title(); ?>
</a>
</li>
<?php endwhile; ?>
</ul>
<?php endif; ?>
<?php wp_reset_query(); // Restore global post data stomped by the_post(). ?>
Credit: ACF Docs
ACF custom examples get_posts post type WP_Query
