curl --request GET \
  --url https://services.leadconnectorhq.com/locations/{locationId}/customFields/{id} \
  --header 'Authorization: Bearer <token>' \
  --header 'Version: <version>'

{
  "customField": {
    "id": "3sv6UEo51C9Bmpo1cKTq",
    "name": "pincode",
    "fieldKey": "contact.pincode",
    "placeholder": "Pin code",
    "dataType": "TEXT",
    "position": 0,
    "picklistOptions": [
      "first option"
    ],
    "picklistImageOptions": [],
    "isAllowedCustomOption": false,
    "isMultiFileAllowed": true,
    "maxFileLimit": 4,
    "locationId": "3sv6UEo51C9Bmpo1cKTq",
    "model": "opportunity"
  }
}