Buzzer on Arduino UNO
If you don't have the part number it's difficult to tell whats the current consumption of the device at the specified voltage.

So what I suggest is. Be sure it's voltage rating is 5V. Connect a 5V supply to the buzzer by a small time, it should have polarity marking, respect it. If it produces a tone (not a click or something like 50/60Hz hum), its a buzzer (it has its own oscillator and amplifier and transducer).

Being it a buzzer, use a current-meter (a multimeter in the DC current mA scale for example), connecting one point of the multi-meter to the supply, the other to the buzzer, and the other point of the buzzer to the supply, always respecting the polarity. This will show to you what is the average current consumption of the buzzer.

The Arduino UNO probably uses a ATmega168P or ATmega328P, the maximum current per IO pin is 40mA (but the maximum total supply is 200mA, so you need to respect this value with some margin even if the IO pin max current is 40mA).

If the buzzer draw more current than the uC I/O can supply, you can try adding a resistor according to the current, but it probably wont work or work out of the specifications.
A NPN transistor will help you







simulate this circuit &ndash; Schematic created using CircuitLab

A general purpose NPN transistor that can handle the current and voltage can be used, also should have the necessary current gain.