My mom did this post pregnancy with my sister and me and she said it helped. I'm working on it now and I DEF feel it in my thighs after I'm done.
A) Bicycling...without the bike.
Lie flat on your back and raise your legs. Perform a cycling motion. Do this for as long as you can (it won't be much in the beginning). Increase your time by 10 sec (or longer) or by 50 cycles.
B) Jumping rope.
You can either do this with the rope or without. Pretend you have a rope in your hands and jump. Remember to swivel your arms as you jump. Check your progress using time intervals or a number (increase each week by 10-15 etc).
Hope this helps!