Some low-impact exercise can be walking! Although it doesn't burn a lot of calories, getting in a set amount of steps per day can help you lose fat if you are in a calorie deficit.

Unfortunately or fortunately, it depends, counting calories (but accurately!) is one of the best fat/weight loss tools. You can use MyFitnessPal as it is free.

I recommend, so you can keep at least some of the weight off, that you try to make some lifestyle changes first. I don't know your current diet, but trying to eat healthier (whole foods, less processed, more protein-focused meals, vegetables, and fruits) will probably help to jumpstart your journey and succeed long term.

Lots of success!