You have to perform Tawbah for what you have done, since it is not permissible
to have an abortion. You have committed a prohibited act and you have to repent to Allah (Exalted be He). If the fetus was less than 4 months, you would not have to make Kaffarah, just perform Tawbah and do not repeat this evil deed again.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.