Nextgen Widget – Unorderd List Output

I am not very knowledgeable in PHP so I don’t know how to change the output the code to the sidebar widget so it’s in the following format for example:

<div class="ngg-widget">
<ul>
<li><a href="https://charliegirl.me/wp-content/gallery/misc/Misc_08.jpg" title="" class="thickbox" rel="sidebar_306637741"><img src="https://charliegirl.me/wp-content/gallery/misc/thumbs/thumbs_Misc_08.jpg" width="75" height="50" title="Misc_08.jpg" alt="Misc_08.jpg" /></a></li>
<li><a href="https://charliegirl.me/wp-content/gallery/autumn-beach-trip/AutumnBeachTrip_02.jpg" title="" class="thickbox" rel="sidebar_306637741"><img src="https://charliegirl.me/wp-content/gallery/autumn-beach-trip/thumbs/thumbs_AutumnBeachTrip_02.jpg" width="75" height="50" title="AutumnBeachTrip_02.jpg" alt="AutumnBeachTrip_02.jpg" /></a></li>
<li><a href="https://charliegirl.me/wp-content/gallery/autumn-beach-trip/AutumnBeachTrip_11.jpg" title="" class="thickbox" rel="sidebar_306637741"><img src="https://charliegirl.me/wp-content/gallery/autumn-beach-trip/thumbs/thumbs_AutumnBeachTrip_11.jpg" width="75" height="50" title="AutumnBeachTrip_11.jpg" alt="AutumnBeachTrip_11.jpg" /></a></li>
<li><a href="https://charliegirl.me/wp-content/gallery/asheville/Asheville07_04.jpg" title="" class="thickbox" rel="sidebar_306637741"><img src="https://charliegirl.me/wp-content/gallery/asheville/thumbs/thumbs_Asheville07_04.jpg" width="75" height="50" title="Asheville07_04.jpg" alt="Asheville07_04.jpg" /></a></li>
<li><a href="https://charliegirl.me/wp-content/gallery/stock/ExploringLincolnton_02.JPG" title="" class="thickbox" rel="sidebar_306637741"><img src="https://charliegirl.me/wp-content/gallery/stock/thumbs/thumbs_ExploringLincolnton_02.JPG" width="75" height="50" title="ExploringLincolnton_02.JPG" alt="ExploringLincolnton_02.JPG" /></a></li>
</ul>
</div>