How do I get back my bookmark folder?
On your iOS 9 or iOS 8 device: Go to Settings > iCloud > Storage > Manage Storage, then tap your iPhone listed under Backups to see the date and size of its latest backup. Go to Settings > General > Reset, then tap “Erase all content and settings.” In the Setup Assistant, proceed to “Set up your device,” tap Restore from a Backup, then sign in to iCloud. Proceed to “Choose backup,” then choose from a list of available backups in iCloud.

WARNING: Don't continue to the second, Reset, step if your iPhone does not show any available backup sets from which to restore. If you reset your phone and erase all settings without having a backup with which to work, you'll end up losing all your data rather than just bookmarks. If there is a backup set available, you should be okay to proceed with the restore.

More information here:

https://support.apple.com/kb/ph12521?locale=en_US