If a user's Office 365 account is deleted, their OneDrive for Business files are preserved for a period of time that you can specify.
To set the retention time for OneDrive accounts
Open the OneDrive admin center, and click the Storage tab.
Enter the number of days you want to retain OneDrive files in the Days to retain files in OneDrive after a user account is marked for deletion box.
The count begins as soon as you delete the user account in the Office 365 admin center, even though the deletion process takes time. The maximum value is 3650 days (ten years).