getting shared_folder_id

The 'missing_scope' error indicates that while the app is permitted to use that scope, the particular access token you're using to make the API call does not have that scope granted. Also, be aware that just adding a scope to your app via the App Console does not retroactively grant that scope to existing access tokens.

That being the case, to make any API calls that require that scope, you'll need to get a new access token with that scope. Please refer to the OAuth Guide and authorization documentation for more information.