Depends on whether you're alliance or horde. To get past 225 skill, you need a quest. For horde, this is in Hammerfall. For the alliance, it's Theramore. If you find a room with a lot of injured people around (including badly and critically injured), you're in the right place.
To say that the task of rescuing the wounded is not very difficult, the following points can be successfully completed: first, players should stand in the middle of the room, so that they can take care of all the wounded, and they can treat all the wounded without moving. In addition, the seriously injured are preferred, which is indicated in the task tip. However, the task does not require you to save all the wounded. Giving up properly makes it easier for you to complete the task. It is said that the task can be done by two people, so the difficulty will be greatly reduced. You can also try it.