(Mirror) Problem with UnityEngine.Networking.ClientScene

I’m following a tutorial on how to make a multiplayer lobby with Mirror, but for some reason it says that the keyword ClientScene does not exist in the current context. I’m just trying to run ClientScene.RegisterPrefab() but I cant do it.

I did using UnityEngine.Networking; at the top and it still comes up with the error.
My version is 2021.3.24f.

Any ideas?