Save the image to your disk. Open it in any editor, even the default one in Windows. Print it. Measure the inner radius. Determine the ratio of that to three inches.
Now, assuming you used the most trivial of image apps, Microsoft Paint, click Resize, and choose the appropriate percentage using the same value for vertical and horizontal. Save it. Print.
Almost any image app will have scaling, and you don't need photoshop quality for a cutting mask.