Hi David,
I'm Cherrelyn, I'm here to help and I understand how upsetting it is when your files are suddenly moved and reorganized without your intention. To get your files back in order on your hard drive have you tried to open OneDrive and go to the folder (like Pictures or Documents) where your files now live. Then select and copy the files or folders you want to move back. Paste them into the corresponding location on your local drive ex. his PC > Pictures. Once confirmed, you can turn off folder backup by right-clicking the OneDrive icon in the taskbar > Settings > Sync and Backup > Manage Backup, then disable the folders.
Let me how it goes' I'm here to help you further.
Warm regards,
Cherrelyn