It's not that simple, one (tractive effort (N)) is a linear force, and the other (Torque (Nm)) is rotational.
Also, torque is affected by gear ratios.
Theorectically, if you multiply the tractive effort by the radius of the tyre, you will get the torque in Nm at the wheel, but this will be different to that at the engine.
Dynolog dynos somehow read torque at the engine, and they manage to do it quite accurately. There is one on the South Coast that read 390nm for a stock standard GT3 and just over 500nm for Gallardo.