If the frontage is a 40 square meter restaurant, six square wires should be enough. Do not use large electrical things. It is possible, the usual usual electricity, there will be no problem.

The square of the wire is the cross-sectional area of the wire, generally does not include its insulation, just the internal copper or aluminum wire, and the wire is round, that is, it refers to the area of the circular cross-section, with square millimeters as its unit. Different square wires, the size of its cross-sectional area is not the same, in the purchase of wires, you can pick according to the power of the appliance, so that you can choose the right wire.