Robin, this
thread is a great idea! I've had those 4 C-sections, so stomach work is tough for me too, even all these years later. In 2012, I cut my portion sizes, limited meat, bread, starches and sodium. No more sodas, mostly water. Changed my snacks from pretzels and chips to gluten free, low sodium options.
Then I bought a fitness cycle and spent the summer on it. Got up to almost 30 mile rides 3 - 5 times per week. That helped me drop 15 - 20 lbs. got sidelined by a severe shoulder injury, but I will get back to it.
One small way to build a bit of core strength is good posture. All day long, use your abdomen to hold yourself in proper alignment. Sounds weird, but it can help. Leads to better breathing too. Another easy thing uses a small weight ball. You set it on the floor beside your foot, then squat to pick it up and pretend you are setting it on a high shelf on the other side of your body. Finish by setting down beside your other foot and stand. Then repeat. It's good for your overall flexibility too.
Also with the weight ball, you sit on the floor, lean back and raise your legs. Touch the floor beside you with the ball, then touch the floor on your other side. 25 reps, then rest.
Three sets of those make a good core workout!
Sorry I don't know the names of those exercises.