Q: hi ive got a question, im backing up my iphone 5s on icloud and im wondering if all my data ( contacts, photos, music, apps, messages) will transfer over to my iphone 6

In addition to doing a backup to iCloud (Settings > iCloud > Backup > iCloud Backup on & Backup Now, I would highly recommend that you go to Settings > iCloud and turn on Contacts and also turn on Photos > iCloud Photo Library (and anything else on Settings iCloud that is of importance to you). You can then use a computer and log in to https://www.icloud.com/ and verify that the Contacts, Photos, etc are actually synced to iCloud. You will not be able to view or verify the backup but you can view that data that you turned syncing on for.

The following also may be helpful: Transfer content from an iPhone, iPad, or iPod touch to a new device - Apple Support