كيف يمكنني أداء صلاة الجنازة على أبي المتوفى منذ ست سنوات؟

The time for prayer over your father has passed, after a long period and the prayers of the Muslims over him. We advise you to make abundant supplications for him, as it has been authentically reported from the Prophet, peace and blessings be upon him, that "[he left behind] a righteous child who supplicates for him." If you are able to do a good deed or give an ongoing charity on his behalf and dedicate its reward to him, that would be better.