A:
You should
make up for the days you failed to fast due to your illness because now you have recovered from your illness. Allah (Exalted be He) says:
...and whoever is ill or on a journey, the same number [of days which one did not observe Saum (fasts) must be made up] from other days.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.