Answer
$f(0) + f '(0)x + \frac{f''(0)x^{2}}{2!}+\frac{f'''(0)x^{3}}{3!}$
Work Step by Step
As $f$ can be differentiated $3$ times at $0$, we use the definition of the Maclaurin series
$p_n(x) = \displaystyle\sum_{n=0}^N \frac{f^{n}(0)x^{n}}{n!}$
for $N=3$ to find the Mclaurin polynomial:
$p_3(x)=\displaystyle\sum_{n=0}^3 \frac{f^{n}(0)x^{n}}{n!}=f(0)+f '(0)x+\frac{f''(0)x^{2}}{2!}+\frac{f'''(0)x^{3}}{3!}$
