Hello
Did your try the following:
STEP 1
Right-click on the Windows "Start" button, and open the Windows Explorer application.
STEP 2
Click the "Tools" option, then click "Folder Options."
STEP 3
Click the "View" tab, then uncheck the "Hide Extensions for Known File Types" checkbox. Click the "OK" button.
STEP 4
Navigate to the BAK file and right-click on the file.
STEP 5
Click "Rename" in the context menu. The file name, along with the file extension, is highlighted.
STEP 6
Move the cursor to highlight only the ".BAK" file extension, and type either ".XLS" or ".XLSX," depending on the version of Excel was used to create the file.
STEP 7
Double-click on the renamed file. If the file is an Excel file, the data will open in an Excel spreadsheet.