Fusion Drive to 970 Evo Plus.

M.2 SSD’s are not the same as Apples custom blade SSD’s So no you can’t use the blade connector for the Samsung EVO SSD.

Your system offers two connections the custom PCIe/NVMe blade interface as well as a SATA III (6.0 GB/s) interface. While the blade interface is the faster interface being custom does make things a bit harder. Here’s a good guide on the Apple SSD’s The Ultimate Guide to Apple’s Proprietary SSDs.

First before you do anything you do need to break the Fusion Drive set following this guide Split Your Fusion Drive Apart

I would hang onto the SATA drive as its still a useful drive if dedicated to a data only drive. I personally would get a 500 GB Apple SSD (SSPOLARIS) as my blade SSD. Making it my Bootable OS drive and hosting all my apps, and leaving the rest of the drive unused! That way the OS and my Apps have free space on the faster drive.

I don’t recommend M.2 SSD’s in Mac’s but if you are head strung on using them then you do need an adapter to convert the Apple connection to the M.2 connection. At least its easy to get to!

So why do you not recommend them? I’ve encountered more failures with them than with the custom Apple SSD’s. Either the drive or the adapter fails. What is hideous here is the adapter will kill the SSD.

Apple also uses some interface lines for other functions that are not replicated on the M.2 SSD’s so when you over fill the drive you’ll encounter a full breakdown unable to recover your files and sleep Mode won’t work correctly.

So while at the get go they look fine as the drive gets used it will buildup problems! I have a full drawer with dead M.2 drives and adapters I’ve pulled out of Mac systems.

Here’s the guide to get to the SSD: Remplacement du SSD du Mac mini fin 2014