Here's one way:
@dirsonly
@nofilenamequoting
Copy MOVE FILE "{filepath$}\*" HERE
The somewhat related Merge Folders script may be of interest, if you want to do more complex logic. e.g. To delete the original folders if they are now empty, without the risk of deleting them if they are not empty for some reason (which would happen if the aaa folder itself contains another aaa folder, so there's still an aaa folder when everything is moved up a level). The DOS-batch rmdir command can also be used as a more simple way to delete (only) empty folders.