“Yorokonde” is an adverb meaning “delighted”, so “delightedly” is a close word. But it is often used colloquially. If you ask me, I’ll be pleased to help you. “Pleased to help you” means “yorokonde tetsudaimasu.” You can reply by saying, “hai yorokonde.” It means “yes with pleasure.” Will you dance with me? Hai yorokonde. There is a famous restaurant chain, where
the staff is trained to say “hai yorokonde” whenever they receive an order from the customer.
Yorokonde is used when speaking with your boss or seniors. If you are assigned a new task by your boss, you can simply reply by saying, “yorokonde!” If you put a smile on your face at the same time, that’d be perfect. If your boss is Japanese, he or she will surely be surprised. They might consider giving you a pay raise. But don’t say it so often unless you really mean it.