Must I return the total salary I received from my previous work in a bank for one year, knowing that I spent all the bank's money and will have to pay the amount from my own money?

If the bank deals with interest (riba) and you were aware of the impermissibility of working there, then the salary is unlawful, and you must give away as charity to the poor, the needy, and for the benefit of Muslims an amount equivalent to what you spent from it. However, if you spent on yourself and you are poor and in need, then you are not required to give away that equivalent amount. But if you were unaware of the impermissibility of working there and have now repented, then you are not required to give away an equivalent amount for what you spent, even if you were not poor; this is based on the Almighty's saying: "So whoever receives an admonition from his Lord and desists, he may have what has already passed, and his affair is left to Allah."