192.168.0.1

> i repeatedly type 192.168.0.1 in the address bar, but I get an error
> message all the time. [...]

   I've never seen that error message.

> [...] What am i doing wrong?

   What are you doing?

> [...] what is the number used to get into the ORBI?

   "the ORBI"?  You have an Orbi?  Has it a model number?  Look for
"Model" on the product label.

> Model: C7800|Nighthawk X4S-AC3200 WiFi Cable Modem Router

   What, exactly, do you have?  What, exactly, is connected to what,
exactly?  (Hint: If a device has different types of Ethernet ports, then
"connected to device" is not enough detail.)

> i repeatedly type 192.168.0.1 in the address bar, [...]

   Of some web browser or other?  Running on some computer or other?
Running some OS or other?  Connected in some way or other to one of your
Netgear devices or other?  Has that computer an IP address of its own?

   Visit http://netgear.com/support , put in your (actual) model number,
and look for Documentation.  Get the User Manual (at least).  Read.
Look for "192.".

   Note that if you cascade multiple routers (for example, connecting
some Orbi router to a C7800 modem+router), then the inner router might
configure its LAN on some non-default IP address subnet.  That's one of
the reasons for using those special Netgear names ("routerlogin.net",
"orbilogin.net", and so on) rather than an explicit IP address.