8940 case can only support oem 8940 board.  The dell psu can only work with Dell proprietary board.  for non-Dell board you can choose any standard intel 500 series mobo to work w Dell cpu ram and ssd.  you of course would need to buy a standard case and standard psu too.
I have a Dell XPS MT 8940 desktop PC. I bought Samsung 970 EVO Plus 2 TB-M.2 NVMe storage as a "second drive" internal to my PC that could provide expansion via High Point Technologies 4zM.2 Port to PCIe 3.0 x16 NVMe Raid Controller. Trouble is my native Dell Motherboard would only support one 2 TB stick in Dec 2020 when I purchased. Now, on Feb 1, 2022, my Dell Motherboard is toast so a good time to replace with the right part to install additional NVMe storage. How do I find out what Motherboard to buy?
Motherboard replacement?