I do workouts with 3-600 jumps a session, occasionally. A million is a large number. It’s an effective way to elevate heart rate, but I’m not sure it’s the best approach for low risk entry to fitness routine. I’d advise starting with assisted press-ups, bodyweight squatting, and assisted pull-ups or rows (if you can find the equipment) and walking, increasing the intensity as your body adjusts. Jumping - and running - are higher impact and may not be the lowest risk option available to start a weight loss journey.