Salaah

Giving kaffaarah for missed salaahs

Q: I would like to know if there is a way I could pay for the missed salahs in my case.

After giving birth my menses cycle did not go normal and was bleeding continuously due to feeding. An Aalimah told me I needed to refer back to my habit previous of pregnancy which was 23 days of tuhr and 5 days of haidh. In this way while doing the calculations almost 2 years later I have discovered I have missed about 400 salah.

With 2 children it may become difficult to perform qadha. Is there a way I could pay for this miscalculation or does Qadha have to be performed?