$ 6to5 source.js -m amd

dest-2.js

// 6to5 source.js -m umd

(function (factory) {
  if (typeof define === "function" && define.amd) {
    define(["exports", "module"], factory);
  } else if (typeof exports !== "undefined" && typeof module !== "undefined") {
    factory(exports, module);
  }
})(function (exports, module) {
  "use strict";

  module.exports = function () {
    return "hi";
  };
});

dest.js

// 6to5 source.js -m amd

define(["exports", "module"], function (exports, module) {
  "use strict";

  module.exports = function () {
    return "hi";
  };
});

source.js

export default function() {
  return 'hi';
};

$ 6to5 --version
3.3.12
$ 6to5 source.js -m amd > dest.js