This code - ${process.env.REACT_APP_BACKEND_URL}/register` - isn't working

I am looking for a freelancer who can help me get React, Node, and Redux working without any issues with the code provided in a Udemy class. I am experiencing installation errors and specifically need assistance with setting up the environment. This is my first time working with React, Node, and Redux, so I will need someone who is knowledgeable and experienced with these technologies to guide me through the process.