How can I present a screen that asks users to confirm their account details upon registration?
you have a function for that "function confirm_form" 

see this link https://api.drupal.org/api/drupal/modules!system!system.module/function/confirm_form/7 


2. add through js 

&lt;?php
    drupal_add_js('(function($){ $(function(){$("#edit-xxxxxx").click(function(){return confirm("confirm do that ?")});}); })(jQuery);', array('type' =&gt; 'inline'));
?&gt; 


refer the above link you will get three different ideas