Can’t scan QR-code with my iPhone.

When I open up Firefox on my iPhone there’s supposed to be a menu there where I’m supposed to click login. And then I’m supposed to be able to scan a QR code. But I can’t find any real menu, and no “login” and I can’t find any scan function anywhere. Does anybody know how to scan that QR code that shows on my Mac in order to sync? I’ve got a iPhone 16 Pro and a MacBook Air from this year, and they’re both updated. I’d very much appreciate if someone knows how to find this scan function on my iPhone. This is starting to be a serious threat to our relationship, me and my phone! Anyway, hope someone knows something, cause I don’t. Very most hopefully wishes, and Best regards from Stockholm-Sweden.