Dell Desktop model 3650 Install 2nd Internal HDD

Just purchased this Dell Desktop.  Attempted to Install a 2nd Internal HDD.  Not seeing a P4 Power connector off the PSU I contacted dell support (all prior Dell Desktops provided 2 to 3 of these add'l Power Connectors)......  Knew it would be a mistake to make the call, did so any way.  Explained the issue, should have been a 10 min call.....I got, you can't install a 2nd Internal drive in this model.  I pushed back, than why have 3 open SATA ports on MBO.  I got, let me check my resources.  The answer, there are power connectors off the PSU...exactly what I told them I couldn't find.  I explained the Factory Installed HDD has a different Power connection than any of my Prior Dell desktops (last one purchased 10 mos ago and it had 3 extra Power (P4) power connectors......this model has a Power cable that connects to the HDD and connects at the other end directly to the Motherboard.  I have never seen this configuration in the past.  I ten got, yet...let me check my resources....call is now 25 mins.  I got there are other power connectors on the MB....they are at the edge...I could find nothing.  I asked, does it require a special cable....let me check my resources.  They said it requires a SATA Power Cable to make the Power connection from the new HDD I wanted to install to the MB.....whats the part Number...they didn't know.  I am now frustrated, the call is 50 mins long...and I just had no confidence I was getting the right answers. 

So my question is, I want to install a 2nd Internal HDD in my newly purchased dell Desktop 3650 (3.5).  I am able to connect the SATA cable but I cannot find a Power source.  Does the HDD in this model use a totally different Power Cable/connectors.  How can a Get Power to the 2nd Internal drive?  If there is a Power connector I must connect on the MB, where exactly is it?  If I must use a special Power cable to make the connection, what is it called and where do I purchase one?  If it takes a Special cable, perhaps I won't be able to install this 2nd HDD...because its a SATA HDD that takes the long multi pin P4 power connector......

Will appreciate the help; Thanks