These are the two processors in question:
Your processor may be soldered to the motherboard. If so, then you cannot change the processor, regardless of any other compatibility.
For a processor upgrade, you must contact Dell and ask them what processors are compatible with their BIOS. Only they can provide this information.
For any upgrade, the upgrade processor must be socket, BIOS, and chipset compatible.
Additional info - look at "Package Specifications" in the link I provided. This is where the SOCKET information can be found.
There are two sockets supported. The BGA sockets are different, and BGA means that the processor is soldered to the motherboard.
The PGA988 socket would allow the upgrade processor to be used, provided it is supported by the DELL BIOS.
Now, my personal opinion - on a machine this old, you would be better off getting a new or newer machine that is supported, specifically if an upgrade to Windows 10 is in your future plans.
Sorry I cannot be of more help.
This message was posted on behalf of Intel Corporation