Issues with uploading

When I tried to upload, it just said\/\/ "Arduino: 1.6.6 (Windows 8.1), Board: "Arduino Uno" Warning: platform.txt from core 'Arduino AVR Boards' contains deprecated recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{build.path}/{archive_file}" "{object_file}", automatically converted to recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{archive_file_path}" "{object_file}". Consider upgrading this core. WARNING: Category '' in library EEPROM is not valid. Setting to 'Uncategorized' WARNING: Category '' in library SPI is not valid. Setting to 'Uncategorized' WARNING: Category '' in library SoftwareSerial is not valid. Setting to 'Uncategorized' WARNING: Category '' in library Wire is not valid. Setting to 'Uncategorized' Sketch uses 450 bytes (1%) of program storage space. Maximum is 32,256 bytes. Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 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." Any help?

Is the Ports menu under Tools greyed out? If so , it's a driver problem. If you can select a port, try another that's listed. If it doesn't list another port, go to your device manager and see if the board is listed there. Note if there is a '!' on the icon.

Estou com um problema no meu arduíno NANO, com o erro erro arduino avrdude stk500_getsync() not in sync resp=0x00 , já tentei de tudo mas não consegui resolver, poderia me ajudar?

Why did you post in this thread? Your problem isn't even related and you speak a different language. Scroll down the forum and please find your language and post there.