How to convert a 10-Watt solar panel into 3v & 3 amp?
From an ebay auction for a 10-Watt solar panel:



Though it's not easy to see, look at the specifications.

(1) 10W is the maximum power, i.e., expect considerably less under less than optimum conditions

(2) The output voltage at maximum power is 17.3V, far more than the 3V your device requires.

(3) The maximum current output is about 0.72A, far less than the 3A your device requires.


  will it work ?


Only in movies where, evidently, any power source will magically have the correct voltage and current to run any device in a pinch.

The lesson here is that the maximum power rating is just that, the maximum power the panel can produce.

As Chris Stratton points out, unless your device can handle the nominal output voltage of the panel and can work over a wide variation from that nominal voltage, you'll need to connect the solar panel to an efficient DC-DC converter with the proper voltage output and current capability for your device.