The terms watts and ohms refer to different electrical principles, so there is no direct way to convert between them. A watt is a measure of power, and an ohm is a measure of resistance. A voltage source produces power, while a given load absorbs it.
High resistance components, such as incandescent light bulbs, convert the current that is passed through them into light and heat. An amplifier has a rating of watts per ohm. This rating refers to the power drawn from the amplifier when used with a speaker of a specified impedance, which is also measured in ohms.