When trying to open Prefab in Unity for editing, another application launches

Hello all,

Came back to Unity after long time and decided to play a bit with it. Unfortunately I stuck at the point where I would need to edit my prefab. While instructions are straight forward how to open it, but when I do Microsoft 3d viewer opens up. I was trying to open .fbx model and I understand that Windows has default application preferences in the settings, but the problem is that I have no clue to what I should change .fbx extension in order to open Prefab mode in Unity. If I change default app from 3d viewer to Unity.exe it simply launches unity hub... so I am in the limbo here :D