Can't upload and I don't know why

I know virtually nothing about arduino and programming. I got a robot that needs its firmware updated , I was told to open a sketch that i downloadd and upload it to the board but I keep getting an eror that said:
Arduino: 1.6.5 (Windows 7), Board: “Arduino Uno”

Sketch uses 20,588 bytes (63%) of program storage space. Maximum is 32,256 bytes.

Global variables use 1,183 bytes (57%) of dynamic memory, leaving 865 bytes for local variables. Maximum is 2,048 bytes.

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x21

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x21

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x21

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x21

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x21

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x21

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x21

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x21

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x21

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x21

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”
enabled in File > Preferences.
I’ve followed the troubleshooting guide for this issue but still cant seem to make it work… I’m running IDE ver. 1.6.5 on windows 7 with an UNO board

Have you checked you have selected the correct serial port?

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