If i fly business class or fly first class will this help prevent dvts?

Possibly: If you are able to elevate your feet to near heart level, the chances of venous stasis leading to DVT go way down, and this is easier in the larger seats in business and first class.

Flying and DVT: It is generally felt that having more leg room when flying will aid in preventing blood clots during the flight. The reason for this thought is that bending the knee will impede the return of venous blood behind the knee which could lead to the development of a blood clot. This certainly sounds reasonable so, if possible, the move leg room the better when flying.