How do I get my storage from my iPhone XR on the iPhone 6?

iCloud has 2 independent functions. iCloud backups, and iCloud sync. It’s confusing because they both have the same name prefix. But they have no connection with each other. Go to Settings/[your name]/iCloud. You will see a bunch of switches. When you turn on a switch that data type will sync to iCloud. If you do this on multiple devices that share an Apple ID the selected data will sync to all of those devices.

You can also turn on iCloud Backups. This will back up your phone every night if the phone is plugged in, connected to Wi-Fi and locked.

But note that anything that you sync by the first method will be excluded from the iCloud backups.

I'm not sure what you mean. Your device storage will always be the same. The iCloud storage that you pay for helps to keep your devices in sync and to share photos.

Learn more: https://support.apple.com/en-us/HT206504

You are going to need to buy more iCloud storage. You've pretty much used up the 50GB of space you're paying for in the cloud. It's clear you don't understand the difference between iCloud Storage and the fixed amount of storage on your iPhone.

iCloud Storage let's you sync data, to iCloud, which can be accessed from any Apple device you use with the same Apple ID. That has nothing to do with the physical storage on your phone. According to your screenshot, you are just about of space in iCloud, having used most of the 50GB of iCloud storage you pay for. This is going to stop you from being able to sync more data (backups, photos, messages, etc.) to the cloud.

No. You only have one iCloud. It is tied to you and is shared amongst all of your devices. You do not need to use iCloud, but you have almost 50 GB in storage in the cloud and that will take up 50 GB on your new phone, leaving you with little space (if that 64 GB is your new phone storage size). Since you have mostly pictures in the cloud, you can optimize photos on your device (settings > photos) to reduce the storage size of photos on your phone. Originals are kept in the cloud (which is also almost full so you should upgrade it is you plan to continue to use iCloud)

If your XR isn't syncing with the cloud, it is likely because you have used up almost ALL of your iCloud storage you're paying for. You are paying $.99/month for 50GB. You are almost completely out of space in the cloud. The next tier up is 200GB for $2.99/month. If you want to be able to sync ALL of your data between ALL of your devices, it's time to move up to the next level in iCloud storage.

Yes. That's your iCloud storage. I still don't understand your original question. What are you trying to do?

You are NOT paying for iPhone storage. An iPhone will never have more storage than it did when you bought it. You are paying for iCloud storage that is used for syncing and backing up.

Provided you signed into your Apple ID and have your iCloud settings turned on it will sync.