You'll need to find the specs for post mount spacing to compare to your caliper but generally calipers are all post mount with adapters to make them work with IS mounts. Your caliper is one of these. If you unscrew the caliper itself from the shallow cradle like adapter that actually bolts to the mount on the fork the resulting bare caliper will fit onto a post mount fork and be in the proper position and spacing to fit the standard small disc size of 160mm.

And the guys are right that those Suntour forks won't be any sort of upgrade. If you're just looking at a replacement then fine. But an upgrade they are not.