Use get_comments_number() to retrieve the value.
<?php comments_number( $zero, $one, $more ); ?>
Displays text based upon number of comments: Comment count zero - no responses; comment count one - one response; more than one comment (total 42) displays 42 responses.
<p> This post currently has <?php comments_number( 'no responses', 'one response', '% responses' ); ?>. </p>
You might want to have a title above your comments section that includes the number of comments. This example shows how to do that and have all the strings also be translatable.
<h3> printf( _nx( 'One Comment', '%1$s Comments', get_comments_number(), 'comments title', 'textdomain' ), number_format_i18n( get_comments_number() ) ); </h3>
comments_number() is located in