I assume the WHOLE garden is 12m x 12m and the garden path divides it into two plots.

So, the whole area is 12x12=144

And the path is 12m long and 2m wide, so its area is 12x2=24

The area of grass is just the area of the garden minus the area of path, ie 144-24=120 square meters

(But I would order about 130 square meters, as you may lose some turf when cutting it to fit LOL)