Hi
Apple Pay is available:
On eligible devices, which include iPhone 8:
In selected countries:
If you are within one of those regions, then check that your iPhone region is set accordingly:
On your iPhone, go to: Settings > General > Language & Region > Region.
Then follow all of the required steps here:
Set up Apple Pay on your iPhone, iPad, Apple Watch, or Mac - Apple Support
Note that it is only possible to add supported payment cards from participating banks or stores within those countries.
More information:
Apple Pay participating banks in Europe - Apple Support
Apple Pay participating banks in Canada and the United States - Apple Support
Apple Pay participating banks in Asia-Pacific - Apple Support