Hi akshitsharma‌,

This computer has 3 M2 PCIe ports:

-Two in size 2280 that work at 4x
-One 1 in size 2242 running at 2x

Yes, the PM961 will work.

Here you have some of the compatible SSDs for this system:

SSD, 1 TB, Non Encrypted, PCIe34, M.2, 22mm/80mm/3.73mm, NVMe, Three Level Cell, Toshiba

SSD, 256GB, Non Encrypted, PCIe34, M.2, 22mm/80mm/2.38mm, NVMe, 512MB, Hynix Semiconductor Inc.

SSD, 1TB, PCIe34, 80S3, 22mm/80mm/2.23mm, NVMe, 512MB, Toshiba, (Class 40, XG5).

SSD, 128GB, Non Encrypted, SATA3, M.2, 22mm/80mm/2.38mm, 512MB, Hynix Semiconductor Inc, (SC311).

SSD, 512GB, Solid State Drive, P34, 80S3, SMSNG, PM981.

SSD, 1 TB, Non Encrypted, PCIe34, M.2, 22mm/80mm/3.73mm, NVMe, Multi Level Cell, LiteOn, (CX2A).

SSD, 256GB, P34, M.2, 22mm/80mm/2.38mm, Samsung, (PM951).

SSD, 512 GB, Non Encrypted, PCIe34, M.2, 22mm/80mm/2.38mm, NVMe, 512MB, Samsung, (PM961).

SSD, 1TB, Non Encrypted, PCIe34, M.2, 22mm/80mm/3.8mm, NVMe, Hynix Semiconductor Inc, (PC300)