Use code tags, please Using code tags properly
Take a look at doc: Unity - Scripting API: Physics.OverlapSphere
You need one more argument, since how would you overlap sphere if you have just pos?, there is also radius needed Physics.OverlapSphere(Vector3 position, float radius)
“in Video Tutorial that script is working perfectly and fine”
Are you sure you didn’t missed one more argument in this funtion?
This is common mistake of beginners - they don’t look at code carefully enough and don’t read error either.