How to get more than the 16 Analog INs on a Arduino Mega for using like 24 piezo sensors i bought an Arduino Mega2560 and flashed it with usbmidi. So now it comes up as a midi device.

I need more than those 16 analog ins to be able to put all my 24 piezo sensors into it to receive midi signals from it. I still have no idea how i have to put the piezo pieces into the arduino but also no clue as how to get more than those 16 analog slots. Any way to use the digital inputs as well or do i need some extension shield or so? I'm a total beginner with arduino...
You can customize a controllino on their page
https://www.controllino.biz/controllino-myplc/
I just looked at it and it seems you can get 24 analog outputs.

Don't know what the cost is though.