All categories and products are gone

While I don't recommend manual edits of database-backup files, feel free to use this guide as an aid.
http://www.zen-cart.com/wiki/index.php/Developers_-_Database_Schema#Table_List_Ordered_by_Data

Most times people make mistakes or assumptions that they don't need certain data, and then end up with a messed-up database. That's why you'll very seldom see us clearly answering any queries about "exactly which tables to import to do xxxxx".

It really does sound like user error. Or malicious nonsense by someone not trustworthy on their end. I suggest a careful refreshing of training, and a reminder that passwords should not be disclosed to anyone not properly trained on using the system.

And make sure backups and restores are working properly.

NOTE: Moving this post out of the hack-attempts forum.

ok i think i might have been cutting the file in the wrong place.
I will import everything but small sections at a time. I just need to be sure where each full "block" of code begins and ends.

does each block begin with DISABLE KEYS and end with ENABLE KEYS?

/*!40000 ALTER TABLE address_format DISABLE KEYS */;

--
-- Dumping data for table address_format

LOCK TABLES address_format WRITE;
INSERT INTO address_format (address_format_id, address_format, address_summary) VALUES (1,'$firstname $lastname$cr$streets$cr$city, $postcode$cr$statecomma$country','$city / $country'),(2,'$firstname $lastname$cr$streets$cr$city, $state $postcode$cr$country','$city, $state / $country'),(3,'$firstname $lastname$cr$streets$cr$city$cr$postcode - $statecomma$country','$state / $country'),(4,'$firstname $lastname$cr$streets$cr$city ($postcode)$cr$country','$postcode / $country'),(5,'$firstname $lastname$cr$streets$cr$postcode $city$cr$country','$city / $country'),(6,'$firstname $lastname$cr$streets$cr$city$cr$state$cr$postcode$cr$country','$postcode / $country');

/*!40000 ALTER TABLE address_format ENABLE KEYS */;
UNLOCK TABLES;

yay! I did it!

phpmyadmin kept timing out so i decided to try the SQL backup query window in Zen Cart and it accepted the file in two parts.

*sigh

what a big relief. now I'm glad I have all those product images saved.

many thanks for all your help and patience.