How do I find my phone if it is dead

There isn't a way to electronically locate a dead phone but you may be able to see its last location before the battery died. In order to see the last location, "Send Last Location" would have to have been turned on in Settings in the phone before it was lost. The description in Settings for that is "Automatically send the location of this phone to Apple when the battery is critically low." The location would not be available if the phone is offline because someone turned it off or because it doesn't have an internet connection, but only if it is off because the battery was low. The additional requirement is that the location is only shown for 24 hours. If all of those conditions are met you would see the last location in Find My iPhone. There is some information on that in Get help with Find My iPhone - Apple Support