It is not quite clear to me what the question is. However, you can use Plots as follows:
using Plots; pyplot()
x=range(-2,stop=2,length=100)
y=range(sqrt(2),stop=2,length=100)
f(x,y) = x*y-x-y+1
plot(x,y,f,st=:surface,camera=(-30,30))
with result:
Here, st is short hand for seriestype (or something similar). Keyword camera sets the camera/viewing angles. I have used the default heatmap.
If you want to plot contours, you can plot contour lines (st=:contour) or filled countours (st=:contour).