بسم الله الرحمن الرحيم
As much salah you have missed it is mandatory to make qaza of them. It shall not be dropped by kaffarah. Hence you should estimate it and offer the salahs which you have missed. You can make the intention saying that you are offering the first Fajr salah among all your missed salahs and then the salah after it till the last one.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.