Where is the power source? Monitor came with no cord and cannot locate the power source input.

I am not sure exactly what type of monitor you are referring to.
But if it's a computer monitor.....

Since I do not know the specific brand and model I can not give you exact location. However there has to be a power input port some where on the back of the unit. It may even be set back up under the back end.
It is a female type port with three prongs in a roughly triangular shape.
It is identical to the power cord used on desktop computers.
It may also be that it originally came with the power cord attached internally but has been pulled out.
If you are referring to another type of monitor or you still are unable to locate it please repost with specific details regarding the make and model.
Hope this helps.

On the back of the monitor you should find three prongs that plug onto the female end of the power cord. The monitor power cord will look the same as your computer cord.