Transfer my farm from an Android to an iOS device and vice a versa.

The  only  way to transfer your farm from an iOS device to an Android device (or vice versa) is by using a Facebook account . You need to have access to both your iOS device and Android device to do this. 

To transfer your farm, your iOS account needs to be connected to the correct Facebook account. For Android, open Silk Road and connect your farm to Facebook in the in-game settings by clicking the Facebook connection button.