I would go ahead and start a new build then. Go for something like Ryzen 3 or 5, or a core i5 newer than 5th gen. Pretty much all of those motherboards will have full UEFI support that will allow the card to work. Just don't pick a super cheap motherboard, make sure it's UEFI BIOS (looks fancy, colourfull, mouse support).
Another thing you can do is just replace your motherboard. You will have to source it from eBay or somewhere; you will not find sandy bridge motherboards on sites like Newegg anymore. You would want to look for an enthusiast board like the ASUS p8p67. I recommend doing a rebuild though, that CPU is going to bottleneck you already and it's only going to get worst unless you are playing old games.