You have a pre-built. The upgrade paths on those were limited, those companies felt that if you wanted a higher performance pc, you would have to buy the next model up. So the chances of upgrade were slim to start with. Then there's the actual upgrade cpus themselves, the FX 8320 / 8350 / 8370 which was nothing more than moving from a 95w cpu to a 125w cpu and adding 2 cores. Many/most pre-built pc's did not use motherboards rated for the 125w class cpus, the 95w motherboards were far cheaper.
In a nutshell, there's no upgrade path at all worth considering, only a replacement path. And that's where the fun begins because several things happen there. Not only do you need cpu, but also motherboard and ram and Windows. And it's a one stop deal, there's no partial upgrade. You will need a new copy of Windows as the current Windows is operating under a key bought by the OEM and tied to the motherboard. It's not transferable as it's not yours, it's theirs. You just paid to use it, not own it.
All in all, about the only things transferable to a new build are storage and gpu, occasionally the case. For everything else, you'll need to start from scratch.