How to find .bashrc or .zshrc?
To know which shell are you using, use the following command:

$ echo $SHELL


It will return something like:

/bin/bash


or

/bin/zsh


After you know the shell, if the file .bashrc or .zshrc doesn't exist in your home directory (echo $HOME to find out), just create it.

If you are using bash, you may have a file called .bash_profile where you can put your export command instead (don't know in zsh).