I believe the standard KiCAD installation includes project templates for several of the Arduino boards. Look in {KiCAD_Installation_Directory}\share\kicad\template
If this is a version of the Arduino Pro Mini, those pins are probably NOT on a 50 mil grid. Furthermore, the Arduino Pro Mini modules you get from various manufacturers are NOT mechanically interchangeable due to footprint variations. See threads at Help with importing arduino pro mini, and Meanwell LDD700h schematics - #4 by davidsrsb and at Arduino Blank Shield Available? - #11 by dchisholm
Dale