I backed up my data via iCloud from 6s and data did not transfer to iPhone 11

The answer depends on A) if you had an iCloud Backup B) If not, what iCloud services you had synced with iCloud individually, and C) if you still have access to your iPhone 6s or not.

If you still have your iPhone 6s and it still has all your data visible on there then erase your iPhone 11 and do the Quick Start transfer: https://support.apple.com/en-us/HT210216

If you don't have your iPhone 6s anymore (i.e. you broke it, lost it, or otherwise sold it or returned it to the carrier) then the first step is to check on your iPhone 11 to see if it shows you have a "backup" made at a certain date and time sitting in your iCloud.

https://support.apple.com/en-us/HT204247#backups

If you have such a backup, then you need to erase your iPhone and when it first comes up you can select to restore from that backup.

https://support.apple.com/en-us/HT204184

If you don't have your old iPhone 6s showing all your data, and if your iPhone 11 doesn't show an existing iCloud backup sitting in iCloud, then your last hope isto make sure you are signed into your Apple ID and you have individual iCloud settings turned on for the individual content you have to hope you were previously syncing (like iCloud Photos, iCloud Messages, Contacts, etc.)

https://support.apple.com/en-us/HT207689

If you already have iCloud settings turned on, or you turned them on now but you don't get your old data back then that means your old iPhone wasn't syncing to iCloud and there's no data available for you on iCloud.