If you haven’t the quest requires you to get your rep up with the leveling zones.) (If you have, you just get to turn the quest back in.
Again, Khadgar in the Violet Citadel will have the quest “Uniting the Isles.” There are two versions of the quests depending on if you’ve unlocked world quests on another character on the account. If the character is not a boost, then you’ll need to first unlock Legion world quests on the character. You’ll need to pick up the quest “The Hand of Fate.” That starts the quest chain for Argus. If the 110 in question is a boosted character, then they need to go to Broken Isles Dalaran and talk to Khadgar inside the Violet Citadel.