You need to upgrade to Mavericks (10.9) or above to get an iTunes compatible with the current IOS. Unless you previously downloaded Mavericks and or Yosemite, they are no longer available. The choices are El Capitan or Sierra.
Check that your computer is compatible with Mountain Lion/Mavericks/Yosemite/El Capitan.
To check the model number hold down the option/alt key, go to the Apple menu and select System Information.
Mac mini (Early 2009 or newer) model number 3,1 or higher
Your Mac needs:
OS X v10.6.8 or OS X Lion already installed
2 GB or more of memory (More is better - 4 GB minimum seems to be the consensus)
8 GB or more of available space
Check to make sure your applications are compatible.
Application Compatibility
Applications Compatibility (2)
El Capitan 10.11 Compatibility information
macOS Sierra 10.12: Compatible Apps
Also check to make sure there is a compatible driver for your printer.
Do a backup before installing, preferable 2 backups on 2 different drives.
To check the model number hold down the option/alt key, go to the Apple menu and select System Information.
macOS 10.12 (Sierra) requires one of the following Macs:
Mac mini (Mid 2010 or later) Model 4.1 and higher
El Capitan
How to get macOS Sierra