All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
Zakah is due on the grains and fruits produced by farms. If the farms are irrigated by rain, rivers or springs, then a tenth of its product should be given out as Zakah. If they are irrigated mechanically or by other such means, half of a tenth is due as its Zakah. If the farms are not cultivated, then no Zakah is due on them, and the same applies if what is planted is anything other than grains or fruits. However, if such a product is sold and its price reaches the Nisaab by itself or by adding other money to it, and a full lunar year passes on the whole amount, then Zakah is due on it by the rate of 2.5%.
As for homes and cars, if they are owned to meet the needs of residence and transportation, then there is no Zakah due on them because they are not included in the types of increasable wealth upon which Zakah is due. The Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said about this case, "A Muslim is not required to pay Zakah on his slave or his horse." [Al-Bukhari]
Moreover, scholars have unanimously agreed that no Zakah is due on homes used for habitation, clothing that is worn, household furniture, slaves and mounts meant for service. If the homes and cars are for trade purposes, then Zakah is due on them at the rate of 2.5% of its value, upon having one full lunar year pass.
Based on this information, you have to determine on which items of this wealth Zakah should be paid and count the years – if there are any – for which you did not pay Zakah since the death of the owner, and pay Zakah on them.
Allaah Knows best.