Add shortcode

Hi, I use this plugin for [gallery]

It’s the HTML code on the page:
<div id=”TB_window” style=”margin-left: -213px; width: 426.75px; margin-top: -294px; visibility: visible;”>
<img id=”TB_Image” src=”25.jpg” width=”396.75″ height=”529″ alt=”Duet Bakery Cake”>
<div id=”TB_caption”>Duet Bakery Cake<div id=”TB_secondLine”>Image 6 of 28<span id=”TB_prev”>??< Prev</span><span id=”TB_next”>??Next ></span></div></div><div id=”TB_closeWindow”><div class=”tb-close-icon”></div></div></div>

I want to add shortcode in php – <?php echo do_shortcode(‘….’); ?> in caption block in lightbox image. But I can’t find where it is.

Can you help me find the file please

https://www.ads-software.com/extend/plugins/nextgen-gallery/