Is zakat obligatory on an amount of 3,0 dinars paid to purchase shares in a bank in order to obtain a non-usurious loan, then after five years it became clear that the loan was usurious and the amount was withdrawn, and is this for the past five years?

It is forbidden to deal with usurious banks, based on the Almighty's saying: (And cooperate in righteousness and piety, but do not cooperate in sin and aggression). The profits obtained from shares must be disposed of in charitable causes, as they are unlawful wealth. As for the original price of the shares, zakat is due on it from the day it reaches the nisab, and zakat is not forfeited by prescription.