Where do I Choose what countries I ONLY want to do business with?

I only want to allow One Specific country to do business with.
I don’t want other countries to be able to list, buy, advertise, join, or participate.

Does anybody know where do I choose or select which country/s I allow.
For instance, in one of my other websites, I can choose which countries to accept payment from, or what countries I sell to. my choice is to select all or just one or two. That is in admin in basic free wootheme.

Where do I set this up in Premium Press admin/s I’ve searched everywhere.
I will have this same need in all Themes. It’s essential towards helping prevent scammers or irreverent fake listings from other countries. Because who in their right mind would intentionally use a dating website to meet somebody in Nigeria, or China, if the lived in Russia! ? So It makes sense, to only allow patrons from the same country. and as a sub category the State, especially in my country, as there’s often 3,000 miles from state to state! A long way to travel to afternoon tea 🙂

Are there any suggestions from people that know for sure!
I would be really grateful if who ever answers, doesn’t just paste a line of code to enter in somewhere! 🙂