What is the ruling and method for making up missed Ramadan fasts due to menstruation, given that one does not remember the number of days previously made up, and it is difficult to make up the remaining number?

It is obligatory to make up for all days for which there is doubt regarding their performance, until one's conscience is cleared. If the delay in making up was due to a valid excuse, then there is nothing else required. However, if it was without a valid excuse until the next Ramadan arrived, then in addition to making up the fasts, you must feed one poor person for each day, knowing that the expiation for delay does not multiply with the multiplicity of Ramadans. The obligation to make up the fasts does not fall away except in the case of permanent inability, at which point it transitions to feeding for each day.