Well, very firstly DO NOT store any new data on the hard drive or on the storage medium where you have lots your Excel sheets data as this will overwrite the lost data and cannot be restored.
And after that try to recover deleted Excel files by restoring the previous version
Open This PC/ My Computer> locate the folder where you have saved the deleted Excel files > right-click the folder > select Restore previous versions > and choose the versions that you need > click Restore.