Hi [NAME] welcome to this free user-to-user Alienware laptop discussion forum.  When BIOS does not see the 1TB Samsung 860 NVMe SSD, it usually means that this card has not been correctly installed in the M.2 PCIe Gen3 or Gen4 slot. Alienware x17 R2 Storage options | Dell US.  Please reseat the SSD card in its slot being careful to ensure that it is electrically connected. Alienware x17 R2 - Remove or Install Solid-State Drive (SSD) | Dell US.    Please note that the Alienware x17 R2 laptop does not accept M.2 SATA SSD cards. 
Took my Samsung 860 1TB SSD from my old laptop into the new x17 R2. The SSD not seen in either BIOS or Windows?
x17 R2, Samsung 860 1TB SSD not recognized