I cannot connect my Mac to Ipad and ipad to iphone

Salutations chulong232,

We’re including a few links below with  information on how to use AirPlay - 

Use AirPlay to stream video or mirror the screen of your iPhone or iPad 

You can stream from your iPhone or iPad to a TV or Mac

Stream video from your iPhone or iPad to a TV or Mac

1. Connect your device to the same Wi-Fi network as your Apple TV, AirPlay-compatible smart TV, or Mac.

2. Find the video that you want to stream.

3. Tap AirPlay. In some apps, you might need to tap a different button first.1 For example, in the Photos app, tap Share, then tap AirPlay.

4. Choose your TV or Mac from the list.

To stop streaming, tap AirPlay in the app that you're streaming from, then tap your iPhone or iPad from the list.

You can mirror the screen of your iPhone or iPad to a TV or Mac

Mirror your iPhone or iPad to a TV or Mac

1. Connect your iPhone or iPad to the same Wi-Fi network as your Apple TV, AirPlay-compatible smart TV, or Mac.2

2. Open Control Center:

• On iPhone X or later or iPad with iPadOS 13 or later: Swipe down from the upper-right corner of the screen.

• On iPhone 8 or earlier or iOS 11 or earlier: Swipe up from the bottom edge of the screen. 

3. Tap Screen Mirroring.

4. Select your TV or Mac from the list.

5. If an AirPlay passcode appears on your TV screen or Mac, enter the passcode on your iPhone or iPad.

To stop mirroring your iPhone or iPad, open Control Center, tap Screen Mirroring, then tap Stop Mirroring. Or press the Menu button on your Apple TV Remote.

Some video apps might not support AirPlay. If you can’t use AirPlay with a video app, check the App Store on your Apple TV to see if that app is available.

Find out which macOS versions and Mac models are compatible with AirPlay to Mac and learn how to set up your Mac to be an AirPlay receiver.

You can use AirPlay to send what’s on your Mac to an HDTV that has an Apple TV connected

Use AirPlay to stream what’s on your Mac to an HDTV

1. Make sure your Mac and Apple TV are on the same network.

2. Click Control Center in the menu bar, click the Screen Mirroring icon, then choose your Apple TV.

3. If asked, enter a four-digit code on your Mac.

4. To set whether your desktop mirrors or extends your Mac screen, click the Screen Mirroring icon, then choose Mirror Built-in Display or Use As Separate Display.

Thanks. 

Hey chulong232,

Let's get a little more information to help narrow this down.

Do you have Wi-Fi enabled on the Mac?

Are the devices on the same Wi-Fi network?

Are you trying to use an iPad as an extended display for the Mac?

Are there any updates for the Mac or iOS devices?

This article has more information is you are wanting to use your iPad as a second display for your Mac.

Use an iPad as a second display for a Mac - Apple Support

Thank you for using Apple Support Communities. Have a good one.