JSFiddle - React, Tailwind, and code Playground

HTML

<select id='slc'>
   <option value="1">Producto nro 1</option> 
   <option value="2">Producto nro 2</option> 
</select>

<input type='text' id='campo1' />
<input type='text' id='campo2' />

JavaScript

var element = document.getElementById('slc');
    
 element.addEventListener("change", function(){ 
    var campo1 = document.getElementById('campo1'),
        campo2 = document.getElementById('campo2');
     
     campo1.value = this.options[this.selectedIndex].text;
     campo2.value = this.options[this.selectedIndex].value;
     
 });