Did you reload your motherboard drivers after the OS reinstall? After you do that, make sure that the SATA cable (flat, 1/4" wide) and power cable (flat "L" shaped connector about 1" wide) are connected to each drive. Restart the computer and check disk manager again. If disk manager still doesn't "see" them, download the free version of AOMEI Partition Assistant (https://www.aomeitech.com/pa/standard.html) and see if it can see the drives.