As far as I know there are no Power block in the Modelica standard library, but it's trivial to roll your own:
model PowerN
extends Modelica.Blocks.Interfaces.SISO;
parameter Integer n;
annotation(Diagram(coordinateSystem(extent = {{-148.5, -105}, {148.5, 105}}, preserveAspectRatio = true, initialScale = 0.1, grid = {5, 5})));
equation
y = u^n;
end PowerN;
