From the looks of that spec sheet, you could put the drive in any of those 4 ports. All offer PCIe 4.0 speed.
I assume you made a typographical error and the last one should be M.2_4, not a second M.2_3.
The only caveat is that if you use M.2_4, your SATA port 2 will be disabled. It's very likely you don't have to use that port anyway.
I'd try to put it in the port that was in direct line with a fan for best cooling if possible. PCIe 4.0 drives can run a bit warm.