You’ll want to move the row/columns inside the loop to do this. Perhaps even inside the template part. Seeing as I don’t know what’s in there, I’d suggest this: (notice I corrected your missing ” at the end of div classes and added php start/stop)
<div class="row">
<?php
/* Start the Loop */
while (have_posts()) : the_post();
echo '<div class="col-md-4">';
get_template_part('template-parts/post/content', get_post_format());
echo '</div>';
endwhile; // End of the loop.
?>
</div>
this is fine if there are only 4 items in your row. or your system handles row calculations for you. If it doesn’t you’ll need to move the row call into the loop as well and add item count and then if statements for the 1st and every 4th item after that.