What is the expiation for not praying Fajr for 10 months due to the time, and what should be done about it?

A Muslim has no excuse for abandoning the obligatory prayer as long as he is sane. If you have never prayed them at all, then you must offer sincere repentance, increase your supplications for forgiveness (istikfar), and make up the missed prayers. However, if you prayed them after their time had expired, then you must repent for delaying them beyond their prescribed time without a valid excuse, as this is a grave sin and a major transgression.