What is the ruling on money earned from previous work in the field of accounting and proving usurious benefits, and is it permissible to start a new life with it after repenting from this work?

We hope that Allah accepts your repentance. It appears that you worked for the company unaware of the prohibition. Therefore, there is no sin upon you in benefiting from the salaries you earned before you knew of the prohibition, as Allah Almighty says: "So whoever receives an admonition from his Lord and desists, he may have what has already passed, and his affair is left to Allah."