Question m.2 ssd

- 1 x M.2_SSD (NGFF) Socket 3, supports M Key type 2230/2242/2260/2280/22110 M.2 PCI Express module up to Gen2 x4 (20 Gb/s)

You can use an NVMe drive such as the Samsung 970 EVO.

HOWEVER - The magical NVMe performance will be severely degraded.
For a motherboard that old, don't bother with an NVMe SSD. You'll see no benefit over a regular SATA III SSD such as a Samsung 860 EVO or Crucial MX500.