Router configuration

I have a question about configuring the router. Sometimes when I was configuring the router and I do not know the full command I tried to get help for the commands. Sometimes I got "<cr>", but I do not know what does it mean. What should I write instead of <cr>?

It's not clear which commands you're referring to.  Most home routers use a website interface for configuration.  Larger businesses use commercial Cisco routers which have their own command language for configuration.

Perhaps the manufacturer of the router provides online documentation at their website.  Or perhaps if you identified the make and model number of the router, someone could assist you?

The expression "<cr>" represents a "carriage return".  In the days of the mechanical typewriter, when you got to the end of the line, you would need a <cr> followed by a "line feed" <lf> to position the "type" at the beginning of the next line on the page.

Perhaps the "<cr>" notation is asking you to use the "Enter" key of the keyboard (but I believe Enter key generates "<cr><lf>").