What type of Arduino is this?
It is a version of Pro Mini.
here in DIY MORE shop

The Mini has regulator. Power it over RAW pin with 7 to 12 V and measure the Vcc pin if it shows 5v or 3.3 V.

To determine the frequency, look at the resonator (the component next to pin 2).

EDIT: the resonator markings are hard to read and very cryptic. to determine the frequency you could install Sparkfun boards package. There you can select the different variants of Pro Mini. Upload Blink. If the upload is successful and it Blinks in 1 second intervals, you have the right setting.