customization - How Can I add show_post_count in get_archives_link?

How can I show archive's post count in an customized html output for archive?

//Change Archive List HTML
function change_archives_output($link_html, $url, $text, $format, $before, $after) {
    if ('with_plus' == $format) {
        $link_html = "<li><a href='$url'>"
                   . "<span class='month'>$text</span><span class='number'>$show_post_count?</span>"
                   . '</a></li>';
    }
    return $link_html;
}

add_filter ('get_archives_link', 'change_archives_output', 10, 6);