IIRC, you want a fan with CFM (cubic feet per minute) of three times the cubic feet of your grow cabinet.

Your cabinet's cubic feet are around 31 feet.

Therefore, 3*31=93 CFM should be the minimum rating of your exhaust fan.

Look into getting a squirrel cage fan with 100+ CFM. They are powerful and fairly compact. Durable, too.

You can also lookinto getting a hurricane fan as well, but I don't have any experience with those.