Connecting already infected devices

Hi, I have a situation with infected devices that required me to replace my old router with a Netgear with Armor.

I clicked on a malicious link on my iPhone which infected it, then spread either through my WiFi connected printer or the router. It infected my MacBook and my wife’s iPhone which are connected to the printer.

I bought new phones and a new Windows computer and the new Netgear router.

I was wondering what exactly I need to do to keep my new uninflected devices safe, if I had to connect my infected devices to do a last backup of files.

Will connecting infected devices on the guest network be safe? Will I receive a threat warning on the Nighthawk app if I do? Can the infected device infect the Netgear router without me knowing?

Thanks for your help!