Hello! Unfortunately, it is not possible to upgrade the storage capacity of an iPhone XR. The storage is built into the device, and it cannot be upgraded or replaced. If you need more storage, you will need to purchase a new iPhone with a higher storage capacity.
The iPhone XR comes in three storage options: 64GB, 128GB, and 256GB. If you have the 64GB model and need more storage, you may want to consider upgrading to the 128GB or 256GB model.
The cost of a new iPhone XR with a higher storage capacity will depend on where you purchase it and whether you buy it outright or through a carrier plan. You can check the prices on Apple's website or through your carrier.