Content template for specific page

I have a page ‘edit-collection-item’
I’d like to write some php that would be the content for that page. Only the content; no modifications to header, footer, etc.

I am a developer, but not a WordPress developer. I’ve never customized a theme, but I’ve done some minimal research.

In page.php, I see this line: <?php get_template_part( ‘content’, ‘page’ ); ?>

I created a file page-templates/page-edit-collection-item.php, hoping this would be retrieved by the line above. It had no effect. Clearly I misunderstood.

When I moved it to the same folder as page.php, it became the entire page, not just the content area of the theme. I was not surprised.

Is what I wish to do possible? If so, what file do I need to create inside which folder?

Thanks!