I have been attempting to use my PS3 to rip some a blu-ray movie to see if it can be done.
When you purchased PS3 and those BluRay disks, you agreed not to do this. Unless you have obtained permission to try, from the copyright holder, then your actions may be against the law in your jurisdiction.
You should also realize that LQ has rules about helping people to break the law.
Note that BluRay disks come pre-damaged by DRM - merely pulling the data is not going to be sufficient.
To find out the location of the external drive with a terminal, you can use the ls command to verify the path.