Installing new PCIe m2 SSD on MacBook Pro 2014 I have a MacBook Pro Retina 2014 with a bad hard drive and recently found out that I can use a PCIe m2 SSD with it on macOS High Sierra. 

I purchased a Samsung EVO 970 and an adapter to use in the internal Mac SSD slot. I also have a PCIe m2 to USB enclosure that I used to first allocate a FAT32 partition on the drive. I also made a bootable USB macOS High Sierra install disk using a virtual Mac. Now I have the EVO 970 installed in my Mac and the boot drive. The boot drive boots to a Utilities screen with options to install macOS etc. 

I formatted the EVO 970 installed in the Mac as a Mac OS Extended (Journaled) disk with the GUID Partition Map scheme. I then proceeded to use the Install macOS option, but I am unable to click on the 970 EVO drive because it says I am missing firmware for this drive. 

I have not updated this Mac past Mac OS X El Capitan before and I am trying to install macOS High Sierra so my Mac will boot from the new SSD. 

What am I doing wrong?
start again:
format the new ssd when still outside the mac (you need an cable to usb). Forget all software that came on the disk: all has to go with the format.
Now use a clone app on the mac, like CarbonCopyCloner, to make a clone of your actual disk with everything on it to the still external disk.
When that is ready, shutdown the mac.
Restart while holding the Alt/Option key: the startup menu is displayed: choose the new external disk: when it starts correctly and all is well:
shutdown again, open the mac, take out the "old" disk and put in the new disk, be very careful with the connectors.
Close the mac correctly, startup normally and are ready to continue where you were.
EDIT: it may be that the ssd connection is soldered: then of course you can not do it what I explained.