A good source to get the sandpaper is the 3M #39084 Headlight Restoration Kit (about $15). It comes with progressively finer grit sandpaper and foam rubbing pads plus rubbing compounds for the last finishing step. Many headlight restoration kits come with a drill attachment and are called 1 or 2 step. Don't get these. You want a hand application kit with progressive sandpaper grit and fishing compounds. Remember this is wet sanding. I use a spray bottle to keep the surface wet and a micro fiber towel to continuously wipe off the dust.
Hard to tell from the pic, but for a small are like that, you might try machine and polish 1st to see it some or most will buff out. I've seen some amazing improvement for initially pretty ugly scratches using this.