Since the base of the rectangular prism is a square, then;
length = width = 3cm and height = 15cm
Then;
[tex]\begin{gathered} V_{rectagular\text{ prism}}=3\operatorname{cm}\times3\operatorname{cm}\times15\operatorname{cm} \\ V_{rectagular\text{ prism}}=135cm^3 \end{gathered}[/tex]Thus, the volume of the prism is 135 cubic centimeters