Hi KooHyun,
Using the ListObjects action and pairing it with the GetObject action would indeed retrieve multiple objects. For the Key attribute, you would provide the S3 Object's name as it is displayed in your Amazon S3 Bucket or use the Key attribute from the ListedObject entity from the ListObjects action.
Be aware that the relative path towards the file you want to retrieve needs to be included in the Key attribute in your GetObjectRequest object. For more information on S3 object key names, please refer to AWS user guide.
Some ideas to order the list of S3 Objects, you can:
Hope this helps!