Disabled phone need itunes but unable to download itunes to mac OScatalina 10.15.1

My daughters iphone has become disabled. i got rid of my laptop (which had itunes) and i know have a new MacBook Air. I think that i need to install itunes but I am unable to install itunes on to mac OScatalina 10.15.1. it needs an older version (10.13.99) to install itunes.

how can i get around this to re-enable my daughters phone.