@zung102 I hope that’s not your actual DuckDNS API token you posted above. Make sure to regenerate your API token if so. You can do that from the top-right of the DuckDNS website, next to your email address, there’s a button to let you “recreate token”.
Caddy doesn’t ship with DNS plugins. You need to download a build of Caddy with that plugin added to use it. See this article for details:
When posting your config and logs to the forums, please use code block syntax. There’s a </> button to help you do that; you need to use triple-backticks on their own lines, before and after the text. This is important so what you post isn’t misinterpreted as other content, which makes it very difficult to read.