How do I find my server?

The 'server' is the state that you were in. If you don't remember the state number then I am not sure if there is a way to find it without loading the game. Did you save / bind the game to an external account such as facebook, game center, google play? If so you can reinstall the game on any device and start a new game. Then log into the same external account to hopefully see your previous saved game with the start number listed.