missing stage frame files

I am using Premiere Elements version 13 on a WIN 10 PC. I started a large project several years ago but had to leave it for a while due to some health issues. However, during that hiatus I had to upgrade my PC from 8.1 to 10 and also (a while later) rebuild WIN 10. Probably 90% of my PE13 editing has been done on WIN 8.1 originally so it (hopefully) has survived a couple of re-installs. I've tried to ensure all data files have been backed up right from the start - using Windows native "file backup" and my own manual backup using an external H.D., however, PE13 seems to use a variety of data files and they do not appear to be all in common directories ("folders") and sub-directories so some may have eluded a critical backup. Recently I attempted to pick up where I left off with the big project and discovered that the program couldn't start because it couldn't find the (raw) *.mts files. So I did a manual search and found them in a very odd 6 levels down sub-directory (perhaps due to my using a program to eliminate duplicate picture and video files about a year ago that didn't run perfectly?) and copied them into a new directory where PE13 can access them now. BUT, now when I try to open an existing project PE13 asks for the "stage_frame.png" file - which I can not find anywhere on my PC or in the backups. This brings to mind a couple of questions: 1. does this mean all of the videos I have created are now useless? 2. Is there any way to recreate the missing files? 3. If I were to upgrade to a current version of PE is there any chance whatsoever I could "recreate" the videos into useable projects using the .prel files from PE13 (which are preserved on the PC)??  Any and all suggestions will be GREATLY appreciated.