How to show NBT Tag in an item description and in a GUI [SOLVED]

Hello,
I recently made something, with a NBT Tag but I need to show the tag inside a GUI (for a machine) and I need to show the NBT Tag in an item description.
I know we can't do it without coding ourselves, but if you know how I could do that, then I could code it with your help and directions.
Please, if you can help, comment.