Id say you fit into a 2-3 years of front-end experience. I mean its always better to up-sell yourself when applying, if they ask you can specify your situation, with as much a positive spin as possible, for example: “I actually have 5 years of total experience, as I was doing X but limited experience using React, I only started using the framework recently and have achieved Y”.
React is still a relatively new technology, so having limited experience is OK, if you have relevant experience.
I’d definitely focus on understanding how a front-end React app, or any “web-app” would connect/communicate with a back-end. As regardless of front-end framework, odds are your front-end will be “talking” with some back-end, and knowing how that work is pretty important for any complex app now-a-days. A good step would be build a simple full-stack app yourself just so you get your hands dirty and get a good perspective on the entire stack as a whole, rather than just a part of the whole stack. I wouldn’t focus to much on the back-end technology beyond getting something working quickly and easily, but the communication between the front-end and back-end is what I’d focus on. If your using React, then it would be a good time to gain experience with the framework in a realistic environment too.