This article will show you how to restore archived submissions.
Who can use this feature?
System Administrators | Owners
Instructions
Navigate to Modules, then Content, and then Form Center:

Select the category the form is in:

Select Go to Archives:

Find your form and select Actions:

Note:
You will want to ensure you pick the item that has the form icon.
Select View Archived Submissions:

Select Actions on the submission you want to restore:

Select Restore:

Note:
You can select Actions for the form and select Restore All Submissions to restore all the archived submissions for that form:

Click OK to confirm:

The submission will automatically be restored