Check if that partition exists in the "Disk Management".
Hold the "Windows" key and press the "R" key. Run dialog box will appear.
Now type diskmgmt.msc and press Enter.
"Disk Management" will be opened.
If you notice a partition without a drive letter then right-click on it --> Select
"Change Drive Letter and Paths..." --> Click on "Add" button --> Add --> Select
the drive letter --> Click on OK.