I recently purchased 200 gigabytes of storage in icloud for $2.99 a month. I want to transfer stored data from my iphone 6 plus to the cloud but don't know how. I bought the expanded icloud for music and phone data. many thanks for your feedback..
iCloud stores data in many different ways so to explain about just transferring stored data would need more input on what you'd like to store.
There's nice instructions from Apple that you could read on the iCloud help page but just to break it down to you first of all what you write about the music which I believe you're referring to iTunes Match which has nothing to do with your iCloud subscription plan and has a limit of 100,000 songs and some other minor limitations.
Now about the iCloud subscription, you could setup in the iCloud settings under Backup that your phone should backup your phones content to iCloud at regular intervals which is explained here and you just need to make sure that you check on or off those apps you'd like to include or exclude getting your backup and that could be achieved by tapping into Storage within your iCloud settings then select the Manage Storage and under BACKUPS select your iPhone which should say underneath its name "This iPhone" there you'll be able to toggle them on and off.
The next thing is iCloud photo library where your device automatically uploads all photos and videos to your iCloud account which is all explained here, I personality love it knowing that my captured moments are always safe which is somewhat safer than having it only backed up at your regular iCloud backup intervals since this happens constantly while you're connected to WiFi.
And finally there's iCloud Drive where app developers could choose to save some of your data there and you could choose to disallow certain apps from accessing them (they could only access these data known to developers as iCloud Container) and if you have a Mac this comes in useful since you could save your files on your iCloud Drive on your Mac and access them on your iOS devices and vice versa.