How can past prayers, performed without ghusl after masturbation, be made up, knowing that the questioner only recently learned about the obligation of ghusl?

We ask God to enable you to repent from this reprehensible habit. You must make up the prayers you performed without purity if you experienced a wet dream and semen was discharged, and you did not perform ghusl out of ignorance of its obligation. This is done as a precautionary measure and to absolve oneself of responsibility.