How do i write a function to be able to read and display these specific readings?
That looks like a JSON string, so start by feeding it through a JSON node to convert it to a javascript object. Then there is 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.
