I have a computer with an Asrock Fatal1ty X470 Gaming K4 in it. I am wanting to up grade my SSD from an older 240 GIG sata 3. To a ultra M.2 PCIe gen3 x4. From everything I can read it takes a M key on the Ultra M.2 PCIe gen3 x4 or the other build in slot that takes a M.2 PCIe Gen2 x2. SO my question is, do I have to use a M key or can I also use a B+M Key?