Hi RDWEB,
I agree with bharath, you need to break the inheritance of the folder and provide access to users you need.
Choose the folder->Files ribbon, choose Shared With->Advanced:
Then Stop Inheriting Permissions, after that you can set unique permission for the folder.
Note: do not remove user from the group, that will remove the user's permission of all site collection, just remove the group and provide access to users you need.
Please remember to mark the replies as answers if they helpPlease remember to mark the replies as answers if they help.
Have a nice day!
Best Regards,
Lisa Chen