I recently bought an Arduino Nano and when I try to find it in the Arduino IDE I cannot find it. please help. This is the error I receive when i try to upload a sketch, avrdude: ser_open(): can't open device "\.\COM3": The system cannot find the file specified.
What is the USB interface chip on the board? FT232, or something else? If something else, you need to locate the PC driver for it.
And also check that you have a power & data USB cable, and not a power only USB cable.