How to update type of existing field to geo_point?

Hi I have an existing index which has location inside the property address which is like below -

"location" : {
              "properties" : {
                "lat" : {
                  "type" : "float"
                },
                "lon" : {
                  "type" : "float"
                }
              }
            },

But I wanted to convert it to geo_point and I tried with below code -

{
  "mappings": {
    "doc": {
      "properties": {
        "address.location": {
          "type": "geo_point"
        }
      }
    }
  }
}

and getting error -

{
  "error" : {
    "root_cause" : [
      {
        "type" : "resource_already_exists_exception",
        "reason" : "index [myIndex/jjUU55BJQrOb1GA4nvO3VA] already exists",
        "index_uuid" : "jjUU55BJQrOb1GA4nvO3VA",
        "index" : "myIndex"
      }
    ],
    "type" : "resource_already_exists_exception",
    "reason" : "index [myIndex/jjUU55BJQrOb1GA4nvO3VA] already exists",
    "index_uuid" : "jjUU55BJQrOb1GA4nvO3VA",
    "index" : "myIndex"
  },
  "status" : 400
}

can someone help me to update the type in existing field -

You can't update an existing field like this. You need to create another index and reindex.