Hi. I'm David, and I'm happy to help you.
OneDrive syncs files between your local device and the cloud. But it doesn't blindly delete files from the cloud just because your local drive is formatted. Here's what happens:
Before formatting: If you delete a file locally while OneDrive is running, it will sync that deletion to the cloud.
During formatting: If you wipe your drive without deleting the files first, OneDrive won't be running, so it won't have a chance to sync any deletions.
After formatting: When you reinstall OneDrive and sign in again, it will treat your device as a new sync target. It will either:
- Download your files from the cloud back to your device, or
- Use Files On-Demand, displaying placeholders locally and downloading files only when needed.
Feel free to ask back any questions.