Hi Helen,
Thanks so much for reaching out!
Yes, the email template is located at wp-content/plugins/event-tickets/src/views/tickets/email.php. You do not want to overwrite the original plugin code, but rather, you should make a copy of that template in order to edit it safely.
You will want to make a copy of that template and place it in wp-content/themes/your-theme/tribe-events/tickets/email.php.
Here is our Themer’s Guide for more information: https://theeventscalendar.com/knowledgebase/themers-guide/
Depending on what it is that you are trying to edit, you may want to also look at the tickets/orders-rsvp.php template and the tickets/rsvp.php template.
I hope this helps to point you in the right direction, let me know how it goes!
Thanks,
Jaime