Till when does stomach pain will persist after 2 months of appendectomy? The reports are normal, the cause of pain is still unknown!

Other issues. There may be additional underlying problems. Scar pain usually resolves by now. See your doctor, they may need to further evaluate.
Where? Mostly scar discomfort is normal, but it should be minimal. Deeper pain may be due to something altogether different such as kidney stones or endometriosis. See the appropriate specialists.