Hello!
I have some problems with my arduino project. How should I wire 3.5 mm jack port to arduino and then connect mobile speaker to it? Then i want to play some music wav files on this mobile speaker.
Jack port photo
Male jack:
Speaker - 3x AAA 1.5V batteries powered speaker
Please send me some pics or tutorials about how i can wire female jack and sketches about how i can connect everything to arduino.
Thanks for help 
The big U-shaped contact is the ground. The other two are left & right signals. Since you apparently don't have the specs, you'll have to experiment to figure-out which is left & which is right, or connect them both together for "mono" sound from both ear cups.
Do NOT connect the headphones* (or an 8-Ohm speaker*) directly to the Arduino! The impedance is too low and you'll get excessive current and you can potentially fry your Arduino. Or, you might just crash your skech or get otherwise-unpredictable-unreliable results.
"Powered" speaker (with it's own power supply) like regular computer speakers are OK. If that speaker has a power supply or a battery, it's OK to connect it directly.
If you want to connect the headphones without using an amplifier, connect a 200 Ohm (approx.) resistor and a 100uF (or more) capacitor in series. The resistor will knock-down the volume, but with most headphones you'll probably still be blasting your ears...
The Arduino doesn't have much memory for WAV files. Do you know the size of your WAV file? Do you have external memory?
Also, the Arduino doesn't have a true digital-to-analog converter. If you want decent quality audio (voice or music), you need an external DAC.
Or, get a WAV or MP3 shield which has memory plus a DAC, and maybe an amp that can drive headphones.
I've got a SD Shield for Arduino. I just need some schemes about how I can connect this speaker with arduino and play audio file.