Im on windows 8.1 and whenever i click to open the portal bat file it just says steam app id not found if anyone could help me it would be incredibly appreciated

You need to have Steam running and you need to own Portal in your library.

The source unpack version of portal only opens if, before you try to run it ,you:
1.Log into steam and have it running. This way, it can check your steam library.
2.You own portal, thus, have it in your library. If you don't have it, you need to purchase it as the bat file fully needs you to own a legal copy of portal through steam in order to work correctly.