Line numbers in SQL Sever are essential when scripting large queries. Enabling them is fairly straight forward.
1) Open up SSMS and nanigate to the "Tools" section. Select "Options" from this section.
2) Within your options window navigate to "All Languages" and select "General". You will see an option for "Line Numbers". Select this option and hit OK.
And thats it. Line numbers should now be available for your queries.