HOw can I find my phone if the battery is dead?

Your iPhone will need electrical power to connect to the internet and report its position. This will not be possible in your case because the battery is dead.

Axel F.

You physically look like it. You can’t use a cellular connection if it is not powered on and connected to the internet.

If you have turned on "send last location" then you can go to www.icloud.com and see where the last one was seen. Maybe it can give an indication. But otherwise it is not possible as the phone is not online.