Files missing from a video file

Download https://elements.envato.com/digital-development-isometric-concept-7V4F228 and when i open the after effects file, it says:

  1. After Effects: this project must be converted from version 13.2 (Windows 64). The original file will be unchanged.
  2. After Effects warning: 29 files are missing since you last saved this project.

So what should do above the missing files?