What libraries / modules should I use and learn to become node.js developer in 2019?

I expertise in front end development. Now, I have quit it and sitting freely. I just want to become a back end developer. And I have choosen node.js.

But while learning node.js I also need to look in other modules, packages or libraries. So, can you suggest me mostly used that I must learn? Any other suggestions regarding back end development using node.js are welcome.

The target should be get the job quickly type as a back end developer in a most challenging environment.