Based on my research, please check the days OneDrive files retention that administrator set for deleted users.
- The default is 30 days, if the user was deleted within this times, you can restore the user and all their data from the Microsoft 365 admin center.
For more, please refer to "Restore a user", and "Step 4 - Give another employee access to OneDrive and Outlook data". - But if the user was deleted more than these days, the user will no longer appear in the Microsoft 365 admin center, and please try to use PowerShell to restore the OneDrive. If you could restore the OneDrive to an active state, then you may assign an administrator to the OneDrive to access the needed data.
For more, your may refer to "Restore a deleted OneDrive",
As this issue involves admin center which is not supported on Q&A forum currently.
To better help you, I would also sugget you post a new thread on Microsoft Answers community --- Microsoft 365 or Office 365 for admins.
Thanks for your understanding.
If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.