Sketch uses 924 bytes (3%) of program storage space. Maximum is 30720 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
avrdude: ser_open(): can't open device "\.\COM3": The system cannot find the file specified.
Cross posting is against the rules of the forum. The reason is that duplicate posts can waste the time of the people trying to help. Someone might spend 15 minutes writing a detailed answer on this thread, without knowing that someone else already did the same in the other thread.
Repeated cross posting will result in a suspension from the forum.
In the future, please take some time to pick the forum section that best suits the topic of your question and then only post once to that forum section. This is basic forum etiquette, as explained in the sticky "How to use this forum - please read." post you will find at the top of every forum section. It contains a lot of other useful information. Please read it.
You need to select the port of your Arduino board from the Tools > Port menu.
If you have multiple ports in the menu and don't know which is your board, Try this:
With the Arduino board unplugged from the USB open the Tools > Port menu and note the listed ports. If the Port menu is gray and disabled then that means there are no ports available.
Close the Tools > Port menu.
Plug in the USB cable on the Arduino board
Wait a little while for the Arduino board to connect
Open Tools > Port, the new port on the list is your Arduino board. In some cases it will have the name of the board next to the port name but this doesn't happen with all boards. If the Port menu is gray and disabled then that means your Arduino board didn't install correctly. You may need to install a driver.
Sketch uses 860 bytes (2%) of program storage space. Maximum is 30720 bytes.
Global variables use 15 bytes (0%) of dynamic memory, leaving 2033 bytes for local variables. Maximum is 2048 bytes.
An error occurred while uploading the sketch
avrdude: ser_open(): can't open device "\.\COM3": The system cannot find the file specified.
This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.
Because you have selected COM3 which is not the COM-port of your Nano. COM3 doesn't even exist on your machine... ( "cannot find the file" refers to the COM-port, that's because the error was written for linux systems on which everything is a file).
Aka, find out on which COM-port your Nano is (tip, that's the one showing up in the "Port" menu when you plug it in) and select that
