- Add script before closing body tag
<script id="dsq-count-scr" src="//SHORTNAME.disqus.com/count.js" async></script>
- Add the link where-ever in the page you want and Change SHORTNAME
<a href="URL OF THE PAGE#disqus_thread"># COMMENTS</a>
COMMENTS will change automatically to number of comments.
You can use it on product detail page as well as in product list page.