Auto numbering textbox once i hit enter key

my target is when is when I type “1” on my textbox then hit enter key, the other textbox will be automatically do a numbering. For example:

I have 3 textboxes, once I type 1 on the first textbox, the other 2 textboxes value will be 2 and 3 and so on. How can I make this work?

<input type="text" value="" readonly class="form-control" placeholder="" required id="auto" name="lb" />
<input type="text" value="" readonly class="form-control" placeholder="" required id="auto" name="lb" />
<input type="text" value="" readonly class="form-control" placeholder="" required id="auto" name="lb" />

Answer

We need to not have readonly on the first field

I prefer to delegate and IDs must be unique

const form = document.getElementById("myForm");
form.addEventListener("keypress", function(e) {
  const tgt = e.target;
  if (tgt.classList.contains("form-control") && tgt.type === "text" && e.code === "Enter") {
    let val = +tgt.value;
    const inputs = tgt.closest("form").querySelectorAll("input.form-control");
    for (let i = 0; i < inputs.length; i++) {
      inputs[i].value = val;
      val++
    }
  }
})
form.addEventListener("submit", function(e) { e.preventDefault() });
<form id="myForm">
  <input type="text" value="" class="form-control auto" placeholder="" required name="lb" />
  <input type="text" value="" readonly class="form-control auto" placeholder="" required name="lb" />
  <input type="text" value="" readonly class="form-control auto" placeholder="" required name="lb" />
</form>

but if you only want the first field to work

const inputs = document.querySelectorAll(".auto"); // I changed the id to a class
const first = inputs[0];
first.addEventListener("keypress", function(e) {
  if (e.code === "Enter") {
    let val = +this.value;
    for (let i = 0; i < inputs.length; i++) {
      inputs[i].value = val;
      val++
    }
  }
})
<input type="text" value="" class="form-control auto" placeholder="" required name="lb" />
<input type="text" value="" readonly class="form-control auto" placeholder="" required name="lb" />
<input type="text" value="" readonly class="form-control auto" placeholder="" required name="lb" />