Electrical plug for 2007 17 in MacBook Pro location of ?

Left side, by the screen hinge.

Its a shallow connector, with a few pins.

You need the MagSafe charger and attached cable.

See the following for what the power connector looks like (from Identify your Mac power adapter - Apple Support )

I don't have that model but every MacBook Pro that I have had, the connector (shown on the left side of the photo below) connected on the left side of the Mac and closest to the bottom of the screen when it is in the open position. It connects and is held in place magnetically.

85W MagSafe Power Adapter with "T" style connector

• 15-inch MacBook Pro models introduced in 2006 through 2009
• 17-inch MacBook Pro models introduced in 2006 through 2009