How do i report a stolen phone to apple

Apple does not get involved with lost or stolen phones, so no need to report this to Apple.

However, you would want to report the loss to your carrier, so they can "blacklist" the phone to not allow another user to use the phone.

Regarding a replacement phone.....If you have AppleCare+ Theft and Loss Insurance on your phone.....start the claim process here:

iPhone Theft and Loss Claims - Official Apple Support

Additional info here:

If your iPhone or iPad is lost or stolen - Apple Support

Watch out for scams that claim that your phone has been found.....and you just need to provide a bit more information so the phone can be returned to you. A message like this will never come from "Apple" or "Apple Service".

You don’t, unless you subscribed to AppleCare+ with Theft and Loss coverage. And if you did you should have received a contract that explains how to file a claim, or use the link on this page→iPhone Theft and Loss Claims - Official Apple Support

Note that claims will only be honored if Find My was enabled on the phone and it was not in Airplane Mode when it was lost.

And here is additional information→If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Beware of a common phishing scam: You may get a text or email from “Apple” or “Apple Security” (or sometimes “Police”) saying your phone has been found and to click on a link to see its location. This is NEVER from Apple or from law enforcement; it is from the thief or fence to steal your Apple ID and identity. Delete any such message without responding to it. Apple never gets involved in lost or stolen devices→Avoid phishing emails, fake ‘virus‘ alerts, phony support calls, and other scams.

iPhone Theft and Loss Claims - Official Apple Support