What should I do after I donated money with the intention of perpetual charity (sadaqah jariyah) to help orphaned girls get married, and then learned that helping orphaned girls marry is not a form of perpetual charity?

If you have paid a charity to help with the marriage of orphan girls, you are not entitled to retract it once it has left your possession and the recipient has taken hold of it. You will be rewarded with the reward of ongoing charity if you intended it, and a hindrance prevented its completion.