Using EX6100 with a New Router

Hello,

I purchased a new Linksys router and want to use the 3 EX61000 extenders with this router.  However, I can't seem to make the extenders work.  I try factory reset but the same old information appears on my network.  I keep reading the instructions on line that talk about the Genie and logging into http://www.mywifext.net.  I don't think I've ever seen the Genie software with any of my 3 extenders.  Every time I try to log into the url given, all 3 of my browsers (Edge, IE, Chrome) indicates that the page can't be displayed or reached.

Are these extenders now useless?

Thank you.