How do I sync my iPhone, iPad, and MacBook Pro to have the same content?

To enable the synchronization of files, contacts, email, notes and other data between your devices, you'll need to sign into the same Apple Account (Apple ID) on each device and enable those item in iCloud settings.

Intro to syncing your Mac and your devices - Apple Support

Sync content between your Mac and iPhone, iPad, or iPod touch - Apple Support

You can synchronize data using iCloud synchronization, and/or connections to the same email accounts.

Connections to shared email accounts can also provide shared access to associated calendars.

nonozec wrote:

my MacBook Pro doesn't have the same contents as my iPad and iPhone.

how do I connect all three products ?

my iPad and iPhone work together . the MacBook doesn't load the same contents .

What contents?

Yeah, what contents? My devices don't all have the same apps on them, so I wouldn't expect them to all have the same content. Yes, I have turned on the iCloud sync.

However, stuff like contacts and notes (if they're on all of your devices) should have the same content.

Although you can run some iPhone and iPad apps on Apple Silicon Macs - if developers allow it - Macs generally use, and work best with, applications designed for them.

Sometimes a family of related applications will have a common name (e.g., Pages, Numbers, Keynote, Photos, Safari) but there will still be separate iPhone/iPad and Mac versions.