Question Which type of SSD need for this?

Any NVMe or SATA based M.2 SSD of size 2280, 2260, or 2242 will work. PCIe version doesn't matter, but a PCIe 4 NVMe SSD will only operate at PCie speeds

EDIT: Further inspection of specs says that the M.2 slot operates at PCIe 2.0 x2 speeds. Still not as fast as most NVMe SSDs can operate at, but it won't really matter.