It sounds like you mistakenly copied the contents of the SCEN folder into your SAVE folder.
Disclaimer - please don't take the following instructions as condescending - my only intent is to be as thorough as possible.
Some possible things to try:
1. If possible, copy the entire SCEN folder from OneDrive back to your WitP:AE directory instead of copying individual files. I don't use OneDrive myself, so I cannot provide more specific instructions on how this is accomplished.
2. Make sure you named the 'new' scenario folder exactly as SCEN - not SCENARIOS, etc. One reason it's better to copy the whole folder from OneDrive is that it eliminates the possibility of naming the new folder incorrectly.
3. Make sure you copy the SCEN folder into the main War in the Pacific - Admiral's Edition directory. Is it possible that you have installed it to more than one location? You might want to search your hard drive(s) just to make sure.
4. Take and upload screenshots of your file structure so we can get a better sense of what has happened.
Last Resort Options:
5. Since you seem to have copied the contents of your SCEN folder into your SAVE folder, you could copy the contents of the SAVE folder into the SCEN folder. Not the most elegant solution, but in theory it should work if in fact all the SCEN files are in the SAVE folder. Probably a good idea to make backups of both folders before you do this.
After you make a backup of the folders, an easy way to copy the files is by doing the following: open the SAVE folder. Press the Ctrl and A keys together to highlight all the files. Press Ctrl and C keys to copy all the files. Navigate to the SCEN folder. Press the Ctrl and V keys to paste all the copied files into the SCEN folder.
6. Make backups of the SCEN and SAVE folders, try uninstalling and re-installing WiTP:AE, and then re-transfering the files from OneDrive.
So you have a point of reference for comparison, here are some screenshots of my game install:
Main directory:
SCEN folder:
(FYI not everything is visible in this screenshot)
SAVE folder:
(FYI not everything is visible in this screenshot - I happen to have the 'archive' and 'autosave' sub-directories in this folder as well)
