How to add leading zeros to a numeric field using the ingest pipeline?

I have a field that needs to be a 3 digit field always. so if the field value is 1 it should be coming in as 001 and if its 11 then it should be coming in as 011. I am parsing this field from a different field using the grok processor and when I simulate the document its showing me 3 digit field but in discover its removing the leading zeros from the field.
I am also not seeing the mutate and replace processor in ingest pipeline using which I know can be useful to my case as shown in the below link:

Hey,

just to be sure. if your field should have leading zeros, it must be a string value and cannot be a number. Is this OK for you?

See this example

POST _ingest/pipeline/_simulate
{
  "docs": [
    {
      "_source": {
        "value": 1
      }
    },
    {
      "_source": {
        "value": 99
      }
    }
  ],
  "pipeline": {
    "processors": [
      {
        "script": {
          "source": """
          ctx.x = String.format("%03d", new def[] { ctx.value });
          """
        }
      }
    ]
  }
}

Hello Spinscale,

Yes, I changed the mapping from numbers to text and the values are coming in as needed.

Thank you.