Mac mini Display

I think the following article should provide you with what you need to know:

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

Is should if the following are all true:

• The Mac mini running macOS Catalina or later.
• The Mac mini is a 2018 model or later.
• The iPad is running iPadOS 13 or later.
• The iPad is one of the following models: iPad Pro (any model,) iPad 6th gen or later, iPad mini 5th gen or later, or iPad Air 3rd gen or later.