When you draw the parabola, draw the line and then shade the area under the curve from to the origin. I'm pretty sure that this is the boundary. Imagine rotating this boundary around the x-axis. This is a solid of revolution.
The general way to deal with this is difficult to explain here.
Do you understand theory behind this?
The formula: where is the cross-sectional area as a function of is what you need. See if this tutorial helps you understand how to find the cross-sectional area, and the theory behind this:
In your case the volume should look like this:
The radius of the solid of revolution should be , so the cross-sectional area is . If this is confusing to you, make sure you watch the video I linked. Seeing someone demonstrate this will help you.