It looks like the model 2 comes with the 1st drive as a 5400 rpm HD so it would suggest it is a 2.5" format and the 2nd HD is probably a an M.2 PCIe-type SSD.
Open up the unit and see if there is a "standard" 2.5" HD in it and this SSD will work in it. My laptop had a 2.5" 5400 rpm HD which I replaced with this SSD.
For the next trick, you will need to buy a USB-sata cable and download the free version of drive clone software to replace the current HD.