In theory it would work if it was a generic motherboard that fully complied with the ATX and PCIe specifications, Though you may require a BIOS update to get a 2016 card to work in a motherboard that old; If that's the case it's pretty unlikely Dell will have written a BIOS update for graphics cards that the SFF isn't designed to ship with
The board may also be unable to provide 75W to the PCIe slot; Quite often those SFF motherboards aren't designed for a 75W card because that form factor will never be able to fit one. Half-height cards are limited by spec to draw only 25W from the board. Whether that's the case with your board is unknown, and even if that is true, the GTX980 might be intelligent enough to draw power from the PCIe slots instead of shorting out the motherboard. It's a gamble that could fry both the board and the 980.
Even if you get it working, it will be awful for cooling and a cabling mess. I assume you are determined to do this crazy project though, otherwise you could pick up literally any mITX case and an adequate ATX or SFX power supply to make it work. How come you want to make this particular case work with a GTX980? Something similar in this form factor would be the
FTZ01: