Is there a way to convert CFM (cubic feet of air moved per minute) to NFA (net free area)?

There is no conversion between net free area (NFA) and cubic feet of air moved per minute (CFM).

Unfortunately, there is no conversion between net free area (NFA) and cubic feet of air moved per minute (CFM). They measure two different quantities, one being area (two dimensional surface space) and one being volume (three dimensional cubic space). The parameters for using one or the other are dependent upon which method of ventilation will be used. NFA is used in static ventilation (ridge vents, wind turbines, gable louvers, box vents, off ridge vents) due to the low air speeds associated with it as only small amounts of pressure are used in those systems to induce airflow. With powered ventilation, we switch to airflow due the use of motors.