New to Drupal: How do I identify which .tpl file is associate to a particular view/node/pane etc?

I’ve never used Drupal before and have been given a task of simply adding some CSS classes to a View element on the page.

When I click on the little gear icon and select Edit I am taken to a ‘Details’ page where I see Title, Pane settings, Fields etc, but no indication of which .tpl file I would need to edit to change any HTML.

There is a Theme: Information link in the ‘Other’ section but this lists about 40 .tpl files, none of which seem to actually exist in my theme’s directory.

Can anyone point me in the right direction here?

Many thanks in advance!

Drupal version: 


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