Hello DewayneD,   For cabled hard drives, no backplane, this will be the cable you need:   PN#38NC4 - ASSY,CBL,SAS,PERC,HDD,X4,R250 ASSY Cable SAS PERC HDD X4    
Dell EMC PowerEdge R250 Installation and Service Manual Page 45 Figure 37. Cable routing - 4 x 3.5-inch cable drive configuration with PERC Table 14. Cable routing - 4 x 3.5inch cable drive configuration with PERC What is the part numbers for these cables? 
PERC H345 4 x 3.5 direct drive connection Cable for R250