Adding a navigation menu in a item

Hello everyone,
I’m a new user of omeka and I’m trying to add a navigation menu while displaying an item. Instead of showing all the elements related to the item, I want to add several tabs like metadatas, files and comments. What is the best way to do so ? I added a secondary nav thanks to the public_nav_items() function but I’m not sure about the uri. I created files.php and comment.php based on the show.php in themes/default/items and I thought the uri associated were ‘items/files/’.$id and ‘items/comments/’.$id but it’s not working (error 404). Does someone know how should I do ?
Thank you for your response

Each file has its own id, different from the item one. The url for files are “files/show/$id”.
For comments, there is no route for a specific page. They are displayed via a hook inside the records (items, exhibits, etc.) pages.

Thanks a lot Daniel, you helped me circumvent the problem. I modified show.php in themes/default/files based on show.php in items and added a public_nav_items() function pointing to both files. Thanks again !!