First, you plugin the lightning part to your i6 and you'll see a pop-up which will lead you to download its app.
Then, you can transfer files from i6 to flash drive in the iXpand Drive app.
More details about this step, you choose "copy file" and then "copy photos from phone," in your case, and just select specific files in the next step.
After finishing the transfer from phone, leave the app and remove the flash drive from i6.
Finally, plug in your laptop with the usb end and read the files as usual, viola!
Hope this helps you complete your job. :)