I need to upgrade my iPhone storage

You can't upgrade storage on your iPhone, but you can check and optimize storage on your iPhone

https://support.apple.com/en-us/HT201656

and optimize photo storage

https://support.apple.com/en-us/HT205703

if necessary (e.g. to upload photo's), you can buy more iCloud storage (monthly subscription)

https://support.apple.com/en-us/HT201318

You cannot upgrade iPhone storage without purchasing a new phone. The storage on an iPhone cannot be changed from when it is purchased.