Front A/C - little air flow on all vents

[2001TahoeGuy]

I have a 2001 Tahoe that has little air flow out of any of the front vents. I can adjust the fan speed and hear the blower motor speeding up and slowing down but the air flow remains the same regardless. I can run the AC cool or hot - just no airflow. It's like one of the vent doors is stuck closed not allowing air to flow through. Just wondering which one it would be and how I could get to it to find out if this is my problem.

Thanks