Direct storage access is not possible with iPhone or iPad devices.
Nowadays, you have services like iCloud Drive (native to iOS), OneDrive, and others that allow the use of cloud synchronization between devices.
It might also be possible to copy files to a compatible USB thumb drive or SD card with an adapter. Also, you can use an SMBv2 or SMBv3 file server directly from the iPhone.
An iPhone is considered as an independent computer

Documentation on external devices or servers:
https://support.apple.com/en-ca/guid...h8d8f0f1a0/ios