To start reversing the CO2 emission we would need as many trees it takes to take up the current CO2 emissions and then a bit more.
From what I found you can estimate every m³ (a bit less than 1 American fridge) of Wood stores 1 ton of CO2. Say each hectare of Forest with fast growing trees produces ~ 10m³ per year (more when they are cut down but they need to grow over a decade+. So if they take 10 years that is 100m³ wood yield at the end).
Humanity produced by some estimates 37 billion tons of CO2 in 2020. That means you need 3.7 billion hectare of forest.
The USA has a land area of 157.7 million hectare. So you need an area of 23 times the LAND area of the United States of America just for trees just to HALT CO² at today's level.
How well are fast growing trees growing in the Arizona desert btw?