Dell typically set up precut power cables w exact length.  In 8940 you may expect two power connectors for two 2.5” hdd on upper left side and one power connector on upper right side.  Power cables are proprietary in the sense they do not come from psu but mobo SATA_PWR socket (mobo supplies sata power).  You may already have Dell sata data cables routed to 2.5 and 3.5 bay already. PS although it is officially claimed that Dell does not supply a 2.5 blue caddy in system ordered w/o hdd, I do see quite a few units shipped w the caddy,  consider that a Dell freebie.
I was hoping someone could answer a questions for me. I ordered an XPS 8940 with a 1TB M2 solid state drive. Will this PC still come with the sata cable to add extra hard drives? If so how many power and data connectors are there?
XPS 8940, hard drive cable provided?