I need the original name of the file to appear under the image, audio or video, since in some cases it is impossible to identify it.

Necesito que debajo de la imagen, audio o vídeo aparezca el nombre original del fichero, ya que en algún caso es imposible identificarlo.

You would need to modify/customize the theme you are using if it doesn't do this. Official themes don't.

Here is the link to the general theming tutorial:
https://www.zenphoto.org/news/theming-tutorial/