Welcome back, Tyson! Good to hear that you will have a trainer available soon. Hopefully the gym's trainers have power meters, but I haven't seen many gym bikes that actually measure power. If they don't have power meters, don't worry because you can train very effectively without power. All that really matters is that the resistance setting is repeatable. I have an old Tectrix trainer that I still use quite regularly in my training, even though it doesn't measure power. What it does have is three key features. First, it has a big, fat, comfortable saddle that I can ride for hours without any discomfort. Second, it has platform pedals with straps that I can ride with my running shoes instead of my cleat shoes. Third, it has an indexed resistance setting versus an analog dial. So, I'm able to find the resistance setting that I can sustain for a given duration at a given cadence and use that baseline to set resistance for a ride given my objective for the ride (e.g., 20min at 90% of FTP). In the early days of your comeback, don't worry about how many watts you are doing on your trainer rides. Just focus on your training volume.