What value to use to find complex impedance of a motor?
As the comments suggest, you are confusing power factor (pf) with efficiency.

$$pf = \frac {P} {S}$$

\$S = \frac {P} {pf} = \frac {3000 W} {0.8} = 3750V\cdot A\$

\$S = P + jQ_L = \sqrt {P^2 + Q_L^2}= \sqrt {(3000W)^2 + (2250 VAR)^2} = 3750V\cdot A\$  

Efficiency can also be added, but you'd have to be given current.