Не так ли?
<body>
<input type=number id=Kod min=100 max=999 value=109 onchange='Calculate(this)' data-for=Denomination><br>
<input type=text id=Denomination value=''>
<script>
function Calculate(el) {
var Kod = Math.floor(el.value);
var Value = Math.floor(Kod / 10);
var Denomination = document.getElementById(el.dataset.for);
var pF;
switch(Kod % 10) {
case 9:
pF = Value / 10;
break;
default:
pF = Value * 10 ** (Kod % 10);
}
if(pF >= 100000)
Denomination.value = `${pF / 10 ** 6} uF`;
else
if(pF >= 100)
Denomination.value = `${pF / 10 ** 3} nF`;
else
Denomination.value = `${pF} pF`;
}
</script>
</body>