Silkalns is right.
You can find copyright related code in footer-extensions.php.
To access that you need to access that file via FTP client.
After you login your FTP account,
STEP 1 - Go to wp-content folder in your public_html folder or wherever you have installed wp
STEP 2 - Then Go to themes folder
STEP 3 - Then Go to travelify folder
STEP 4 - Then Go to library folder
STEP 5 - Then Go to structure folder
Here you will see THREE different php files... one of them is footer-extensions.php
On line#67 you will find function : function travelify_footer_info()
This contains copyright footer info.
Hope this will help you.