The dell tech specs has the system with a HD6450 1GB or a HD6350 512MB. The game requires an HD4870 1GB so the HD6450 should run the game but about 4 times slower. IE the HD4870 is 4 times faster than the HD6450. The slower HD6350 probably will not work as it doesnt have 1GB video RAM. Check to see which you have. https://www.dell.com/downloads/global/products/optix/en/optiplex-390-tech-guide.pdf
The dell tech specs has the system with a HD6450 1GB or a HD6350 512MB. The game requires an HD4870 1GB so the HD6450 should run the game but about 4 times slower. IE the HD4870 is 4 times faster than the HD6450. The slower HD6350 probably will not work as it doesnt have 1GB video RAM. Check to see which you have. https://www.dell.com/downloads/global/products/optix/en/optiplex-390-tech-guide.pdf