Then (because you were ignorant of the rule), you just need to make up the missed days only, and feed a poor person per day for delaying the making up (Qadha). That is 750 gms of flour or rice (22.5 kg's for a month), which could be given to a poor person (Food, not money).
Example:
If you missed 4 months of Ramadhan, then you need to fast 120 days (not necessarily continuous), and give 90 kg's of food to poor people.