I need major guidance. This cloudflare thing is really confusing me lol

Hello all. I am new and have several questions on how I should go about deploying my full stack web app. Firstly, I'd like to describe my setup. I have 2 repos: one for the client (react) and one for the server (express). I am using yarn for building as well (cra is a specified framework option but it is no longer being maintained). This brings about the first qquestion. Do I use workers or pages? What is the difference? I have looked it up and found that pages is cheaper? Otherwise most people say they are the same. Additionally, do I host both my server and client on pages? Or how do I manage that? At the moment, I have been experimenting and I tried creating a page on Cloudflare and connected it to my client repo, but i get this error (attached image). Why is it even using node? Can I override this? I dont even have node in my project.json. I'm sure more questions will follow, but this is all I have for now. Thank you!