Water – What type of compression fitting do I need

I purchased a GE PLV1817XSS dishwasher and I am trying to connect the water to to the dishwasher intake, but I'm having trouble finding the correct fitting. The water intake is an unthreaded plastic tube that sticks out the back. The instructions^(Spanish) are extremely vague and simply say to get a 90 degree elbow, but give no indication of what size of anything is needed:

I had purchased a Braided stainless steel water hose which comes with an elbow (3/8" FCM (Female Compression) x 3/8" MCM (Male Compression) 90° brass elbow), thinking that this was all I needed, but I didn't realize that it lacks the compression nut that goes with it.

The outer diameter of the water inlet tube is 14 mm (measured with a vernier caliper), but when I went to a place that specializes in brass, they said they don't have anything that measures 14 mm, since apparently that isn't a standard size. They had one fitting that is 12.8 mm, which is too small, and another that is about 16 mm, which (I think) is too big. Can anybody give me an idea what I need to get the water connected to this thing? Do I need something else besides a brass fitting that might come in different measurements?

I called the support number listed in the manual and they told me that they wouldn't help me unless I paid for a certified technician to do the installation. Thanks, GE.

Edit: Apparently that tube sticking out the back is not the water intake. The water intake is on the front of the dishwasher.