Hi [NAME] Jundiah,   Based on VMWare's HCL reference, R750XS and PERC H755, minimal OS version need to be ESXi 7.0 U3.   R750XS HCL: [URL]   PERC H755 HCL: [URL]
it's basically the title, the server is dell PE r750xs raid card: perc 755 front  hard disks: 600gb SAS when booting the ESXi I don't have the perc as an option when downloading the OS. 
ESXi 6.7 U3 can't detect the perc755 raid card