How do I pair iPhone 16 Plus with 2024 MacBook Air 13?

You can't "pair" them using bluetooth if that's what you mean. That has never been supported and is completely unnecessary.

Handoff, airdrop, continuity, etc. do not require traditional bluetooth pairing.

What is it you are trying to accomplish by doing that?

iPhones and Macs can work together in several ways:

• Through iCloud synchronization (Set up iCloud on all your devices - Apple Support)
• Through connections to shared e-mail accounts (which can have associated calendars)
• Through Continuity features (Continuity features and requirements for Apple devices - Apple Support)
• Through manual synchronization of content (e.g., purchased music) from a Mac to an iPhone
• Through shared subscriptions to services like Apple Music, Apple TV, and Apple Arcade (where most of the stuff that you can access on one device can also be accessed on another)

I see the hosts have re-titled your post to mean something completely different to what you actually asked.

Apologies. They have been notified.