JSFiddle - React, Tailwind, and code Playground

HTML

<select class="your-country">
   <option value="0" data-val="98898">Россия</option>
   <option value="1" data-val="9889811">Краснодар</option>
   <option value="2" data-val="9889822">Екатеринбург</option>
   <option value="3" data-val="9889833">Москва</option>
   <option value="4" data-val="9889844">Новосибирск</option>
   <option value="5" data-val="9889855">Самара</option>
   <option value="6" data-val="9889866">Ростов-на-Дону</option>
   <option value="7" data-val="9889877">Нижний Новгород</option>
   <option value="8" data-val="9889888">Ярославль</option>
   <option value="9" data-val="9889899">Уфа</option>
   <option value="10" data-val="98898100">Тверь</option>
</select>

<div class="your-country_target"></div>

JavaScript

(function($){
        var selectVar = $(".your-country"),
            elemTarget = $(".your-country_target");

        function checkCountry(elem,out){
            $val      = elem.val();
            $data_val = elem.find('[value="' + $val +'"]').attr("data-val") 
            out.text($data_val || "Нет номера" ) 
        }
        $(document).ready(function() {
            checkCountry(selectVar,elemTarget); 
        });
        selectVar.on("change",function(){
            checkCountry(selectVar,elemTarget); 
        })
    
})(jQuery)