Unable to pair my iPhone XR and iPadOS 18.1.1 with my MacBook Air 12.7.6.

If by pairing you mean connecting the iPhone and the Mac so they can work together seamlessly, sharing data and features. This is typically done through Bluetooth or Wi-Fi, depending on the functionality you want to use.

Some common uses for pairing an iPhone with a Mac include:

1. Handoff: This feature allows you to start a task on one device and pick it up on the other. For example, you can start writing an email on your iPhone and continue it on your Mac.
2. Continuity: This lets you answer calls, send messages, or use your iPhone as a hotspot while using your Mac.
3. AirDrop: This enables you to transfer files between your iPhone and Mac wirelessly.
4. iCloud Sync: Pairing ensures that your photos, contacts, and other iCloud data sync between your devices.
5. Apple Music and AirPlay: You can stream music from your iPhone to your Mac or vice versa.

For most of these features to work, both devices need to be signed in with the same Apple ID and have Bluetooth and Wi-Fi enabled. Some features, like Handoff and Continuity, require both devices to be on the same Wi-Fi network.

This may help --> iTunes Finder not Connecting to Mac - Apple Community