Newer 3-way switches are labeled as 'Common' on the back of the switch, next to the Common terminal screw. Secure the traveler wires (black and red) from the 14-3 cable to the brass screws. It ...

The third screw on each switch is a black-colored screw, which is the common terminal. One way to think about it is that your far-end switch has two input lines (the travelers) and one output line ...

In Box 1, disconnect a wire on the old switch and attach it to the correct terminal on the new one. Methodically dealing with one wire at a time will help avoid confusion and mistakes.