Simply follow the steps below to reset your Acer Iconia B1-711
Right from the Apps menu, tap on Settings > and then tap Backup & reset.
Tap on "Factory Data Reset" > and then tap "Reset Tablet".
Tap "Erase Everything" to format your tablet back to factory default configuration.
To locate the reset button in case you cannot access the device's Operating System to perfom a Factory Data Reset via Software Menus, Acer recommends the referencing to the tablet model's User Manual.