List of graphic card

Never mind my previous post about no modern GPUs being suitable at all for your M920s SFF. Although every single decent modern gaming GPU requires a full-height slot and a full-width case, I managed to find an NVIDIA Workstation GPU that would be a great choice for that PC (assuming that you have a power supply unit in that PC that's 400W or higher): The PNY RTX A2000. This GPU is essentially a downclocked version of the GeForce RTX 3060, and is available with either 6 GB or 12 GB of GDDR6 VRAM. Prices (assuming that you'll be paing full price) are $450 and $700, respectively.

I am sorry to tell you this, but your PC's PCI-e card expansion is restricted to very short, very small half-height cards. Unfortunately, all of the good GPUs are full-height cards - way too big for that PC case of yours. Worse, if your case's PCI-e capability is also restricted to half-height backplates, then you're out of luck since any half-height graphics card that's even halfway decent in performance use a full-height backplate.

You'd be better off just completely replacing the entire PC, in this case: Every single GPU that's compatible with your case is either very weak or is badly outdated or obsolete.

Moved to video hardware forum.