Probably large but unfortunately it's not always quite so simple. The length you need will depend on what seat angle you are riding at, how long your stem is, your body proportions, etc.

Most aerobar sizing guidelines put me at a medium but I ended up getting smalls. Because I have long legs for my height, with the original stem I had, my knees would hit the back of the aerobars when standing on a climb so I had to get a stem that was about 2cm longer. But this meant I was too far forward when in the aero position so I got small aero bars about 2cm shorter to compensate.