Owning Multiple Devices and apps

You want to use the same Apple ID on all of your iOS devices. If you do that, you can download all past purchases as long as they still available for download. The message that you are getting seems to indicate to me that you might have signed in with a different Apple ID on the new iPad Mini when you set it up.

You could erase the iPad Mini and start all over again. If you use these instructions, the apps that you have on the phone, should download to the iPad as well as long as those apps will work on an iPad.

Transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support

If all of the apps don’t download to the iPad, you can download them yourself in the App Store. Bear in mind that you must be using the same Apple ID on both devices.

Redownload apps, music, movies, TV shows, and books from the App Store, iTunes Store, and Apple Books - Apple Support

As for the automatic downloads that you found in the settings, if you turn those on, all of the purchases that you make on one device will automatically download to the other device as long as you use the same Apple ID on both devices.

I assumed that you created a new ID, but that doesn’t mean my assumption is correct. However, if you erase the device and follow the instructions in the link that I posted, you should be fine. There will be a point in the setup where you will have the option to enter your Apple ID so enter the ID that you have been using all along.