If the accounting work that involves recording usurious interest is forbidden, is the salary earned from it completely forbidden, or is only a part of it forbidden and must be disposed of?

If your work involves restricting usurious benefits or helping to spend them in ways not sanctioned by Sharia to dispose of them, then the salary received for this is unlawful (haram), and benefiting from it exposes you to the warnings associated with consuming unlawful earnings, such as prayers not being answered and the threat of Hellfire.