How can a woman atone and repent for the years of her life that passed without a hijab?

He who repents of his sin and abandons his disobedience, Allah loves him, accepts him, and forgives him, as He said: "Indeed, Allah loves those who repent and loves those who purify themselves," and "And indeed, I am Forgiving to him who repents, believes, and does righteousness, and then is guided." So, whoever abandons sin, regrets it, resolves not to return to it, and adheres to obedience, has fulfilled the required repentance.