HELP!! M.2 NVME SSD NOT DETECTED IN BIOS & DISK MANAGEMENT BOTH.

Check bios sata operation make sure it is AHCI and not RAID on.

What's the plan here? Use the new SSD as the C: boot drive or just use it for extra storage?

Unless you're going to do a clean Windows install on the new SSD to use it as boot drive, don't change that setting to AHCI if it's set to RAID, or you'll make the PC unbootable.

To change BIOS to AHCI, you have to do it the right way so you don't lose your apps and data:

1. Open Cmd, run as administrator.
2. Copy-paste this command, which will start Windows in Safe Mode the next time you reboot: bcdedit /set {current} safeboot minimal and press Enter
3. Restart the computer and tap F2 to enter BIOS setup.
4. Change SATA operation from RAID to AHCI.
5. Save the change and exit Setup. Windows will automatically boot in Safe Mode.
6. Open Cmd again, as in step #1.
7. Copy-paste this command, which will start Windows in Normal Mode the next time you reboot: bcdedit /deletevalue {current} safeboot and press Enter
8. Reboot and Windows will automatically start with AHCI drivers enabled.
9. Now you should see new SSD in Disk Management but it will to be initialized so it can be used for storage.

If you plan to remove an existing HDD and use the new SSD as boot drive, but want to keep all your files and apps, you should image that HDD after changing BIOS to AHCI (as above). Save the image on an external USB drive.  Macrium Reflect is a useful tool (free for 30 days).  Be sure to create the bootable Macrium USB you'll need to boot the PC. 

Then remove the existing HDD and set it aside. Install the new SSD if not already in the M.2 slot. Close up and plug Macrium USB and external USB drive with the image into PC with power off. Power on and tab F12 to open the menu. Select option to boot from USB.

Macrium will load automatically. Select the image source (external drive) and destination (internal M.2 SSD) and start the imaging...