Yes, you can take Button with you internationally! The power supply that is included with your Button device accepts worldwide voltage. Depending on the country you may need a plug adapter, but a power converter should not be needed anywhere.
Please note that Button is powered through a USB-C port, meaning you could alternatively use a third-party’s USB-C cable, which should be internationally compatible.
If not using the provided power supply, please ensure your power supply is from a trusted brand. The adapter should be electrically certified for 5 Volts DC and is compliant with standards of USB 2.0 or later.