code: public function getGeoIpMappingForCountry($countryCode)
      {
          if ($mapping = $this->_scopeConfig->getValue(self::XML_FASTLY_GEOIP_COUNTRY_MAPPING)) {
              return $this->extractMapping($mapping, $countryCode);
          }
          return null;
      }
docs: Get store ID for country.
  
  @param $countryCode 2-digit country code
  @return int|null