hello is a greeting and in urdu one can use it to ask as kaisay hain aap or kia hal hain or its in commom usage now a days to say hello doctor.Hello is in common use in URDU also it can be used to let some know that you are calling him or her so its sunoo or suniyay, then for How are you is aap kaisay hain ya ap kaisi hain if its for a female.