Reported Speech (Questions)
-When a direct question has word like a word like who, what, how, we use this word in the reported question.
"Where is the post office?" he asked.
He asked where the post office was.
-When a direct question doesn't have a word like who, what, we use if/whether in the reported question.
"Can I send the package by mail?" he asked.
He asked if/whether he could send the package by mail.