This is really a training to power question. As you are new and have a lot of headroom to improve, I would suggest not getting so hung up on hitting a power target for hour-long efforts. Just enjoy riding, ride as much as you can, mix up the intensity so your body continues adapting, and take regular rest days. Consider joining races or group rides if those types of activities would motivate you.

Rouvy automatically estimates a value for your functional threshold power (FTP) as you ride more. This value is crucial to performing the right kind of training with power in the right zones and for the proper duration. But just starting out you will be getting fitter and the numbers won't be all that helpful.