The U.S HHS Office of Disease Prevention and Health Promotion created a generic recommendation for all Americans:
For substantial health benefits, adults should do at least 150 minutes (2 hours and 30 minutes) to 300 minutes (5 hours) a week of moderate-intensity, or 75 minutes (1 hour and 15 minutes) to 150 minutes (2 hours and 30 minutes) a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic activity. Preferably, aerobic activity should be spread throughout the week.
Additional health benefits are gained by engaging in physical activity beyond the equivalent of 300 minutes (5 hours) of moderate-intensity physical activity a week.
Adults should also do muscle-strengthening activities of moderate or greater intensity and that involve all major muscle groups on 2 or more days a week, as these activities provide additional health benefits.
To provide more structured advice, I'd need to understand a few things. First, what do you hope to accomplish from an exercise program? Some common goals might include:
Improve overall health (e.g. lessen risk of heart disease, diabetes, etc.)
Get stronger / Make day to day living easier
Help control weight regain (notice I didn't say lose weight as you can't out exercise a bad diet)
Improve mental health / reduce anxiety & depression
Sleep better / Have more energy
Improve body composition (more muscle mass = more calories burned even at rest)
Look good naked
Next, are their specific activities you like or don't like? Some people hate gyms, others love them. Some people like to "play" to get exercise (think sports/outdoor recreation), while others love the solitude of walking/running by themselves. Basically what I'm asking is for you to do some self-reflection and think hard about what you think might work best for you.
Finally, can you be more specific about what resources you have available? You mentioned a gym (which is not entirely needed), but beyond that? Do you have or can you get:
A heart rate monitor (e.g. fitness watch or strap)
A place to walk outside or access to a treadmill
Other exercise/recreation equipment such as a bike or stationary bike, kayak or canoe, Nintendo Ring Fit Wii Fit, etc.
A set of exercise bands and/or dumbbells,
Sufficient space to workout at home if you don't go to a gym
I'd also really like you to fill out your profile here on Bariatricpal. Details matter. In addition to that, it would be helpful to know some things like:
Your age
How you'd rate your current fitness level
If you have any specific physical or health issues that might impact what exercises/activities you're able to do
In short, the more details you can provide, the more tailored I can make a recommendation.
Best of luck.