If you're using a cmd.exe inside your VS Code (en.wikipedia.org/wiki/Cmd.exe), the default terminal VS Code offers you, then you probably need to add the firebase-tools to your PATH environment variable for it to recognize it.
I probably won't do a good job of explaining what it is, so you can take a look at what the PATH variable in Windows is here. Basically, you're trying to run a package you've installed via npm, but Windows doesn't know where to find that command and that's why it says "Command not found"
Here are some solutions that might help you out with that:
If you're using a cmd.exe inside your VS Code (en.wikipedia.org/wiki/Cmd.exe), the default terminal VS Code offers you, then you probably need to add the firebase-tools to your PATH environment variable for it to recognize it.
I probably won't do a good job of explaining what it is, so you can take a look at what the PATH variable in Windows is here. Basically, you're trying to run a package you've installed via npm, but Windows doesn't know where to find that command and that's why it says "Command not found"
Here are some solutions that might help you out with that:
I think this should sort out the issue you're having, just make sure you restart your VS Code after any changes to the PATH variable
I am still trying to figure out the issue.
Thanks for your help anyways :)