A pinball (mass 94.0 g, radius 1.24 cm) is pressed against a spring (spring constant 137 N/m) compressed by 3.50 cm. ?

Question

After the spring is let go, the pinball rolls along a horizontal surface. What is its speed?

I keep getting the wrong answer and I'm not really sure how else to go about this question.

kx^2 = Iω^2 + 1/2mv^2, was the equation I was using.