Sorry I cannot get these new forums to display what to type.
type backslash( backslash)where backslash= \
Because backspaces also work to escape things here. You should be able to do \\ to get \.
In this case, where the goal it to highlight exactly what is to be typed (including spaces etc.), the easiest way is to put the string between backticks. This is for code and will use a monospaced font with a slightly darker background: \( \)
CommonMark offers a very brief cheat sheet over markdown, and of course also the full specification if you have a lot of time.