image size

Hi, i need some help with the following.
i am not a good coder. so please a little bit of help would be nice.
After a lot of searching, i found this piece of code that worked for me.
As the code on your website did not get any images on my site.

<?php
                              
               
if( class_exists('Dynamic_Featured_Image') ) {
     global $dynamic_featured_image;
     $featured_images = $dynamic_featured_image->get_featured_images( get_the_ID() );
    //If you want to display all featured images you can loop through the image to display them as required
    foreach( $featured_images as $image ) {
        echo "<a href='{$image['full']}'>";
        echo "<img src='{$image['thumb']}' alt='Dynamic Featured Image' />";
        echo "</a>";
		
    }

}
              
?>

What i want is to have a smaller size image.
in my functions.php i have made

add_image_size( 'product_content', 100, 100, true);

but when i change ‘thumb’ in the first code to ‘product_content’
nothing happens

Can you please help me?

greetings

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