Considering menstruation I didn't pray for some days, but it was istihaza, how can I make up those missed prayers now?
As-salamu Alaykum sister,
There are many scholarly arguments for this.
The most popular view is that she has to catch up her prayers that she didn’t perform.
With istihada, she has to do wudu for each salat IF she is still suffering from istihada. If this is a lot for you, trying spreading it out throughout the day?
I hope this helps.