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

Move a user databases

To move a data or log file as part of a planned relocation, follow these steps:

1. Run the following statement.
   
    

   ALTER DATABASE database_name SET OFFLINE;  
   
   

2. Move the file or files to the new location.
3. For each file moved, run the following statement.
   
    

   USE master
   GO
   ALTER DATABASE AdventureWorks2012
   MODIFY FILE 
   ( NAME = AdventureWorks2012_Data, 
   FILENAME = 'C:\Disk2\AdventureWorks2012_Data.mdf'); -- New file path
   
   USE master
   GO
   ALTER DATABASE AdventureWorks2012 
   MODIFY FILE 
   ( NAME = AdventureWorks2012_Log, 
   FILENAME = 'C:\Disk2\AdventureWorks2012_log.ldf'); -- New file path
   

4. Run the following statement.
   
    

   ALTER DATABASE database_name SET ONLINE;  
   
   

5. Verify the file change by running the following query.
   
    

   SELECT name, physical_name AS CurrentLocation, state_desc  
   FROM sys.master_files  
   WHERE database_id = DB_ID(N'<database_name>');  
   
   

tempdb modify size, move file

Modify the size
ALTER DATABASE tempdb MODIFY FILE ( NAME = tempdev, SIZE = 1024 ).
The database will be resized when the server restarts next.
Move the file
ALTER DATABASE tempdb MODIFY FILE ( NAME = tempdev, FILENAME = 'x:\full\path\xxxx\tempdb\file\tempdb.mdf' /*, SIZE = .... */ ) the file will be created in the new path when the server starts next