I don't have "arrangement" tab in my system preference>Displays

The iPad is generally not treated as a "regular" second display, but as a special case using "Sidecar" feature.

Use your iPad as a second display for your Mac with Sidecar - Apple Support

Once your iPad is recognized, it may appear as a second display and be subject to arranging, but not before.

MarieF-D wrote:

I am trying to use an iPad as a second screen/monitor. The instructions said go to System Preferences>Displays and open the "Arrangement" tab. I do not have an arrangement tab.

See if you still have this option >System Preferences>Displays

press the Option key while you're in Displays— You'll get a Detect displays button (bottom right).

there is a checkbox "Show displays in menu bar". If you check it, you get a new icon in the menu bar that has "Detect Displays" as its first option.

Use external monitors with your Mac: https://support.apple.com/en-us/HT202351

If AirPlay or screen mirroring isn’t working on your device https://support.apple.com/en-us/HT204291