Adding missing permission to a folder for the MSSQL$instance account

I had to move the data files from one driver to another. After moving the data files when I brought the database online it gave"Access denied" error and I found out that the reason was that the MSSQL$instance account did not have permission to the data file.
I right clicked on the folder and on the security tab tried to add the user to give the missing permission but could not locate the user. I had to do the following to find the user in the user list

To add the missing permissions
chose the local computer and type in "NT SERVICE\MSSQL$instance