My iPhone 8 Plus camera and flashlight do not work

Start here

If the camera or flash on your iPhone, iPad, or iPod touch isn't working

 but I think you'll need

How to arrange  a repair

First try a Forced restart

https://support.apple.com/guide/iphone/force-restart-iphone-iph8903c3ee6/ios

If no better

You should arrange a repair

https://support.apple.com/iphone/repair/service

or: contact Apple Support 

Anything other than Screen or Battery may be a replacement phone and the price is in the article.

You can see additional service information within the following article:

Prepare your iPhone for packing and shipping