For those having the bug problem like i did (i collect them all but the track was showing that i had 93%), here's how i get it:
1. Go to your games and apps, on the Forza Horizon 3 and choose Manage game
2. Go to your save data, choose it and Delete from CONSOLE
(Only local save! we don't want to restart the game all over)
3. On your X1 go to Settings - Network - Go OFFLINE.
4. Now start the Forza Horizon 3. It should start by you racing a car, then you will choose one car, with this car you will race 2 Exhibition and make a danger sign jump. After this you will upgrade your festival to level 2.
5. Only after upgrade the festival you will be able to search the beauty spots. Follow any guide that you have and collect all the 13 spots. Remember that you are offline.
6. Complete Close the game. Tap Xbox Button
, go to the forza horizon 3 and press menu button
and then close game.
7. Right now you can go ONLINE again. Tap the Xbox Button
and choose Connect to Xbox Live (It will take you to the Network screen, choose Go Online there). Wait until it shows your NAT.
8. Just to make sure that you got you achievement, go to your profile and then achievements. This will pop Backpacker achiev
9. Repeat the step1 and step2 (Go to your games and apps, on the Forza Horizon 3 and choose Manage game, in the save data choose to delete from CONSOLE one more time)
10. After the local save be deleted you can start the forza horizon 3. Your cloud save will be sincronized and you will be able to continue the game from where you stop. And hunt the challenges. And be happy.