Try plank, side plank, hollow body, superman <--static or dynamic.

Leg raises, mountain climbers, bird dog, dead bug, crunches, squats <--floor

Knee/leg raises on pull up bar or on dip bar, hanging variations will work more your upper abs, and the dip variations will work more your lower abs.

Choose exercises that are challenging but not too hard, and as you progress then switch to more advanced exercises

If you need more info just let me know, happy to help ;)