We are travelling to Xian in March.Please advise which airport shuttle bus to take?

Staying at Days Inn City Centre, 99 North Street. Some websites says Shuttle bus Line 2 takes you to Main Railway Station. Some says Line 3. Please advise which is correct, Line 2 or 3? Exactly where does the bus stop at the Railway Stn? When going back to airport, where do we take the bus? Thank you.