The short answer is: ride at whatever wattage is comfortable, sustainable, and enjoyable for you.
Every cyclist has their own unique power profile, power-to-weight ratio, and cycling goals, so it is impossible to narrow it down to a single wattage number. However, if you’d like to get into training and power-based intervals, do an FTP (functional threshold power) test to determine your maximal cycling capacity.
From there, you can input your FTP into a number of training software such as Strava or TrainingPeaks, and they will give you your power zones that you can use to guide your training.