Mafia 3 is going to be a beautiful, visual treat. And consequently going to need a pretty powerful modern PC to run it. This shows with the recommended CPU requirement being a Core i7-3770 3.0GHz or FX-8350. The system memory requirement for top level Mafia 3 graphics is going to be at least 8GB coupled with a GTX 960 or AMD R9 280 with at least 2GB VRAM graphics card. This should let you run Mafia III at around 1080p with 40-60FPS on high graphics setting.
Set in New Orleans 1968, Mafia III is a third-person action-adventure open world game, where you play as a Vietnam vet seeking revenge against the local mob, who murdered your friends.