Dell branded desktop pc, the power supply depends on the model.
many dell optiplex systems have:
4-pin cpu power
no 6-pin pcie power (especially 240w–300w psus)
some higher-wattage dell psus (365w, 460w, or above) include:
4-pin or 8-pin cpu power
6-pin or 6+2-pin pcie for a graphics card
to know for sure, please tell me your dell model, for example:
dell optiplex 3020
dell optiplex 7040
dell precision t3610
dell xps 8940
or send a photo of the psu label or the inside of the pc, and i can identify whether it has a 4-pin cpu connector and a 6-pin pcie connector.