While I’m not a forensics expert, I do know enough to say, there isn’t really enough information to answer this definitively.
Decomposition is heavily affected by the overall warmth of the climate. If you’re talking about a tropical environment, you can realistically be looking at completely skeletonized remains in under a month, while if you’re talking about forested tundra, complete decomposition could take years. This is of course assuming nothing swings by for a snack.
One of the problems with bodies dumped in the wilderness is that you’ve added a free food source. So any of the local wildlife that aren’t squeamish about cold leftovers can make off with parts of your victim. A forensic tech can identify what kind of animals have been feeding, but that rarely provides useful information.
It’s also worth pointing out, the end result of decomposition is scattered bones, not a neatly laid out skeleton that’s a bleach wash away from hanging in some A&P class.
So, no idea. Sorry.