By default, the built-in File Explorer as well as many commercial file manager programs such as Resco Explorer cannot copy files that reside in your device’s ROM. This is because the file binary has been customized for your device so even if you could extract the file out of ROM, it would not be of much use. For more information, see this blog post.
However, if you still want to do this, there is a tool that you can download from here.
You can just run the tool on your device, select a file in ROM to be extracted and choose where to save the file. Notice that the extracted file may or may not work as expected.