I download itunes from apple store,but can't install.

hi

I download itunes from apple store,want install new version,old version is support

Iphone 6 S Plus,but New Iphone 8 Plus can't support old version.

Apple Itunes ask me update.I try many time update also can't update.

So I uninstall itune and go apple store download new version and plug in Iphone 8 Plus still can't/

Why?

I display photo for u looking first.