setting up poweredge T20 drives

Hi, i have 2 samsung 750 500gb evo's SSD's and 2 WD red 3TB hard drives want to run in raid, I have the 2 WD red hard drives attached to sata0 and sata1 ports on the motherboard, the dvd on sata3.  I bought 2 "Best Compute M.2 PCIe SSD to PCIe 3.0 x4 and M.2 SATA SSD to SATA III Adapter Card s" and installed them in the expansion slots 1 and 4.  In the bios the computer doesn't recognize the cards, says all slots empty.  it recognizes the WD reds but of course not the SSD's.  The SSD drives work tried them in sata0 and sata1.  what am i doing wrong?  i want raid 1 to mirror the drives.  My thinking is  an older motherboard the SSD's run faster on the expansion cards.  nothing in manuals says the speed.  thanks

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