Mix format on save VSCode

Mix format works fine if run from the cmd. I’ve followed this to facilitate the implementation into VSC which involves downloading an extension called vscode-elixir-formatter. When I save however:

I have a .formatter.exs in my project directory which looks like:

[
  import_deps: [:ecto, :phoenix],
  inputs: ["mix.exs", "*.{ex,exs}", "priv/*/seeds.exs", "{config,lib,test}/**/*.{ex,exs}"],
  subdirectories: ["priv/*/migrations"]
]

and I’ve checked all the boxes in the VSC user formatter settings. Do I need to tell vscode somehow where my .formatter.exs file is?