Doesn't look like it. The motherboard diagram in the Inspiron 3280 AIO Service Manual doesn't show a CPU socket, and no instructions to replace the CPU. So it is probably hardwired onto the board.

You cannot upgrade the processor unless you replaced the motherboard. Even if you could, that is the upgrade that gives very little added performance if any. You have a laptop-like board and the processor is part of the board. Use it as is. All in ones are not as upgradeable as desktops with replaceable parts. 

See the service manual-

https://topics-cdn.dell.com/pdf/inspiron-22-3280-aio_service-manual_en-us.pdf