The above converter works online only and you do not have to download or install any tool to make it work.
Simply drag and drop your choice of JPG images and it will give you the desired PNG image. Make sure the images are not more than 20 in a single batch. Plus, each image should be maximum MB.
Convert X2Y do not permanently store any of your images on the server. All the images uploaded by you are deleted in the next 30 minutes. Nobody would have access to those.