i had to edit in notepad ++ and the namespace is wrong however on the tutorial i watched my code is exactly the same so why am i getting this name space error and how do i fix it

I have two errors a namespace for "Vector3" I don't know how to fix this or why it is an error since I copied the tutorial I was watching exactly and there are no differences except for the fact that I used notepad ++ and he used visual studio. by the way, I can't use visual studio another issue I'm having is that it cant recognize a local variable named "movement". please help its for a school assignment and i don't wanna fail