Answer
We need to use at least 2 polarizing sheets.
Work Step by Step
If one polarizing sheet is at an angle of $90^{\circ}$ to the original direction of polarization, then none of the light will be transmitted. Therefore, we need more than one polarizing sheet.
If we first transmit the light through a polarizing sheet that is at an angle $\theta$, such that $0 \lt \theta \lt 90^{\circ}$, to the original direction of polarization of the light, then we can rotate the light's direction of polarization by $90^{\circ}$
Therefore, we need to use at least 2 polarizing sheets.
