By using a height of 3.2 units, I modeled the Lego plates in the same way as the standard Lego bricks:
For some other plates (the blue ones) I used the line tool to draw the shape and the extrude modifier with a value of 3.2:

By using a height of 3.2 units, I modeled the Lego plates in the same way as the standard Lego bricks:
For some other plates (the blue ones) I used the line tool to draw the shape and the extrude modifier with a value of 3.2:
