That's a different "All-New X-Men" to the "All New All Different X-Men". I'm not going to be ever be able to say that X-Men publishing is not confusing.
There's not single digital collection of all of these issues.
If you link your Comixology account with Amazon, you can buy Kindle books on Amazon and read them on the Comixology app on the tablet, much cheaper with their current sale, but all these volumes are on both
Or just jump in and get just the Dark Phoenix story collection (#129-137)
(If you know generally who the major X-Men characters are you can pick it up and follow along, but as I said the story is the end to a longer story) https://www.amazon.com.au/X-Men-Dark...313911-3228341
Yeah i realised that wasn't the same series you referred to but i was just highlighting my point of 'jumping in' to a series which is then incorporating a bunch of other ones and crosovers.