How many volts are in 10 amps?

This will depend upon the resistance of the load. You will have to use an Ohmmeter to do this. BE SURE POWER IS OFF when you do this, however. You'll smoke your meter!!.

Then you can use Ohm's Law and the formulas to solve this. However, the easiest way to find voltage is to simply use a voltmeter and measure the source voltage.

There are no volts in amperes! They measure two different quantities. Your question is rather like asking, "How many kilometres are there in a kilogram"!