Ok well first thing first always check the built-in help by selecting the node & viewing the sidebar. Note: not all developers add good help in fact, sometimes there is none. However, the good nodes have decent help.
Another thing is to look at the built-in examples that come with many of the nodes and node red itself. You access the examples with the shortcut CTRL-I
Next a bunch of canned text that should put you in good stead...
first stop...
I recommend watching this playlist: Node-RED Essentials. The videos are done by the developers of node-red. They're nice & short and to the point. You will understand a whole lot more in about 1 hour. A small investment for a lot of gain.
JSON? Sting? Object?
This post should help to clarify the difference between Javascript objects and JSON.
When it is an object, it is REALLY EASY to grab parts of the msg...
There’s a great page in the docs (Working with messages : Node-RED) that will explain how to use the debug panel to find the right path to any data item.
Pay particular attention to the part about the buttons that appear under your mouse pointer when you over hover a debug message property in the sidebar.
Forum stuff...
In order to make code readable and usable it is necessary to surround your code with three backticks (also known as a left quote or backquote ```)
```
code goes here
```
You can edit and correct your post by clicking the pencil 
icon.
See this post for more details - How to share code or flow json
other resources...
- https://flows.nodered.org/ - nodes, readmes, demo flows
- https://cookbook.nodered.org/ - common patterns.
Good luck.
