The Raspberry Pi 3 is powered by a USB Micro power supply that can supply at least 2A at 5V for the Model 3B, or 700mA at 5V for the earlier, lower powered models. Lower current (~700mA) power supplies will work for most basic functions, however are more likely to cause the Pi to reboot if it draws too much power.
Using an adapter such as 1528-1798-ND above will allow you to use a wall adapter with a 2.1mm ID and 5.5mm OD barrel plug to get 5V and 2A and properly power your Pi 3B.
Here is a list of Barrel Plug Power Supplies Digi-Key carries that will work with adapter 1528-1798-ND and provide 5V and at least 2A.
There's also a selection of power supplies which have Type A ports to allow for a standard Type A to Micro-B cable (like those used for phone charging) to be used. Lastly, there are some power supplies which have the a Micro-B plug attached .