list tables in mysql dump

$ zgrep -o '^CREATE.*' database_backup.sql.gz

CREATE TABLE `aa_migrations` (
CREATE TABLE `abcdefg_bar` (
CREATE TABLE `abcdefg_foo` (
CREATE TABLE `abcdefg_images` (
CREATE TABLE `abcdefg_table12` (
CREATE TABLE `abcdefg_table13` (
CREATE TABLE `abcdefg_table14` (
CREATE TABLE `abcdefg_table15` (
CREATE TABLE `abcdefg_users` (

You could also just count them:

$ zgrep -o '^CREATE.*' database_backup.sql.gz | wc -l
9