Where is Earphone outlet on iPhone 8?

No 3.5mm headphone port on an iPhone 8.

The earphones which came in the box, should have a lightning connector.

Or, you can buy this adapter:--> Lightning to 3.5 mm Headphone Jack Adapter - Apple

Regards

Giulio

Hello ~ Take a look here:

Where do I plug my earphones on IPhone8? - Apple Community

~Katana-San~

This choice was made to comply with the IP67 (water resistant) specification, according to the IEC 60529 standard.