backup iphone to desktop

Hi, and welcome the Apple (user-to-user) Community.

Re: how to backup iphone 14 pro Max to my desktop

Wondering which iOS version is installed on your iPhone,

and

whether you want to back up to a Mac or PC desktop.

Apple support have articles online that may help guide you:

For Mac:

How to back up your iPhone, iPad, and iPod touch with your Mac - Apple Support

For PC:

How to back up your iPhone, iPad, or iPod touch with iTunes on your PC - Apple Support

Troubleshooting:

What to do:

If your computer doesn't recognize your iPhone or iPad - Apple Support

or

If you can't back up your iOS or iPadOS device to a computer or restore it from a backup

All the best :-)