Plantation forestry grows about 20 cubic meters per hectare-year [0]. Doug Fir weighs ~600 kg-m3 [1]. 3B US tons / (20x600 kg) per hectare-year = 6,796,166 hectares. Plantation lumber is harvested in 7, 14, and 21 year cuts [0], so to ensure you're always sequestering enough carbon you need 21x6.8 million hectares of new forest to defray the current CO2 production... which is about 551,000 square miles, which is approximately [2] Texas + California + New Mexico... or [3] France + Spain + Italy.
The new forest would still be ~20% of the size of the Amazon rain-forest though [4].