how to add template format in serilog appsetting

Try below:

{
  "Serilog": {
    "Using": [ "Serilog.Sinks.Console", "Serilog.Sinks.File" ],
    "MinimumLevel": "Information",
    "WriteTo": [
      {
        "Name": "Console"
      },
      {
        "Name": "File",
        "Args": {
          "path": "Logs\\log-.txt",
          "rollingInterval": "Day",
          "outputTemplate": "{Timestamp:ddMMMyyyy}.txt"
        }
      }
    ]
  }
}

Thanks