i messed with arduino bootloader

i got this error

avrdude: verification error, first mismatch at byte 0x0000
0x62 != 0x0c
avrdude: verification error; content mismatch

i cant able to upload other program same program is running when i open the serial port
arduino doesn't showing done uploading

i tried troubleshooting by connecting tx and rx and reset and ground
no echo comes in serial port

If loopback isn’t working your USB-to-Serial isn’t working. Time to re-load the firmware on the 16u2.

johnwasser:
If loopback isn’t working your USB-to-Serial isn’t working. Time to re-load the firmware on the 16u2.

oh no! how to do it? i use arduino uno r3 (confusion in soldering 10k resistor)

https://www.arduino.cc/en/Hacking/DFUProgramming8U2

In this tutorial they used uno r1, I have Uno r3

also i cant find select devices list atmega328p in flip software

randomly i choose atmega 16u2 but i got an error

From the error message it appears that your installation of the Flip program is missing some required library. I don’t use Windows so I can’t help much there. I’d Google the name of the missing file.