when i want to upload this erro is shown
Arduino: 1.8.5 (Windows 10), Board: "Arduino/Genuino Uno"
Sketch uses 1938 bytes (6%) of program storage space. Maximum is 32256 bytes.
Global variables use 202 bytes (9%) of dynamic memory, leaving 1846 bytes for local variables. Maximum is 2048 bytes.
avrdude: ser_open(): can't open device "\.\COM3": The system cannot find the file specified.
Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.
This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.