How do you have your levels named/numbered?
Is it 'one scene is one level'?
You could always then use the level name string and then use 'Get String Right' and get the digits that you want from the end of the scene name and save that as an int.
Isn't Load Level Number dependant on the order of scenes that you have in your build settings? It'd probably be more efficent/safe to use Load Level and use a variable, just incase anything changes, then it won't break.