32 missions at about 20 minutes per mission. About 11 hours. But you have to consider leveling is about 2 to 3 times slower than the beta, so you likely be doing some exploring or strikes or pvp to get your character up to the next level of the story. They will also be having a daily story mission also though no idea if it ties into the main story or something like a very mini side quest or something that fills in the world like grimoire cards.