A Microsoft file hosting and synchronization service.
1
What happened to your files on OneDrive, did you delete those files yourself?
2
Log into OneDrive online in a web browser (https://onedrive.live.com/).
Check the Recycle Bin to see if your missing files are available in there.
3
If the files are not in the recycle bin, if you have a Microsoft 365 subscription, click the gear icon at the top right of the OneDrive web page and select 'Settings.
On the left, click 'Recover My OneDrive' and try using that process to recover your files.
4
If that process is unsuccessful in recovering your files, there is no other native process available to recover your files on OneDrive, you will need to use some 3rd party recovery utility to try to undelete and recover the files on your PC.