Q: How to download my data I had backed up on iCloud

If you're asking how to restore to your iCloud backup, this has to be done in the initial device setup process, which requires first erasing your phone.  If you have any newer data on your phone now that is not in the backup that you want to save you'll need to do that first.  When you're done, go to Settings>General>Reset and tap Erase All Content and Settings.  Then go through the setup screens on your phone and when given the option, choose Restore from iCloud Backup.  Be sure it is connected to wifi and your charger as this will take some time to finish.

If that's not what you're asking, please clarify what data you are trying to retrieve.

Ok, tried that and pictures or music stayed away. Had previously accounts, still have passwords, support said not able to retrieve. What's the purpose of cloud if not to save all my data?