Probably meant 15x8?
15 inch is the diameter of the wheel, and 8" would be the width. If you have a tape measure you can easily verify.
Generally for an 8" wheel you don't want to go wider then 10.50" tire. So some tire size options 31x10.50, 32x10.50, and 33x10.50. Bigger sizes will be harder to find, and the 33x10.50 might be hard to find.