Install PCIe cards in your Mac Pro

m2 pcie slot   Dan m2_1 slot

Such motherboards usually have an extra x4 slot connected to the chipset, so in that case you should move your GPU to that slot and install the

2 standard contains variants with up to four PCIe lanes, one SATA 6 Gbs and or one USB port So it is possible to connect PCIe as well as SATA SSDs  2 drives are “keyed” at one end so as to prevent the end-user from inserting them in an incompatible socket PCIe NVMe drives are 'M' keyed SATA ones,

demo slot olimpus 2 slot only has four PCI Express lanes, a quarter of the total generally desired for graphics cards---but the flexibility for this tiny little B650M-HDV · Build for The Most Advanced PC · Optimized VRM Design · DDR5 Memory with Protection Circuit · Reinforced Steel Slot