<input class="input" type="text">
<div id="popup">priv</div>

#popup{
  width: 150px;
  height: 150px;
  background-color: aqua;
  display: none;
}

$("input").keyup(function(){
  const count = $(this).val();
  if (count.length >= 3) {
   $("#popup").show()
  }
})