iphoto file name

Which system version do you have installed on your Mac? What you are seeing below a photo thumbnail will depend on your system version.

• In the earlier versions of Photos - MacOS Yosemite to High Sierra - you are seeing the title below the thumbnails of the photos, or nothing else.
• In macOS Mojave you will be seeing the title below the thumbnails, of the photo has a title, and if the photo has no title, you will be seeing the filename, slightly dimmed. (The best solution, IMHO)
• In the first version of Catalina we have been back to square 1, but the newer versions are again showing the title, if the photo has a title, and the filename, if the title is missing. How to view the titles or filenames below the thumbnails in Photos 5.0 - Apple Community

Only, Photos in Catalina does not use the filename when sorting photos in an album, like Photos 4 on Mojave has done: Sorting Albums by Title in Photos - Changes in Photos 5.0 on Catalina

If you want to find the photos without a title, you can do this with a smart album with the rule "Title is Empty"

To have a truly empty filename, your photos would have a filename starting with a dot. Such files will be invisible, but if you managed to import invisible files, you can find them with a smart album with the rule

"Filename > starts with > . "

You can't have a photo without a file name. You may have some without a Title which is what shows up beneath the thumbnail but it's not the file name. All files on a computer must have a file name and, usually, an extension

If you use the Smart Album File Name is not then keep the file blank you'll get all of the items in the library.

If you what to add the real tile name to the Title under the thumbnail use this AppleScript: Script: Changing the Title to the Filename without Extension.

The script compiled as an application can be downloaded from this tutorial site:  P01 - Applescripts from Photos’ User Tips Compiled as Applications  

Is this what you mean?

This is a New Smart Album.