Vickie, This is a very timely issue for me. Just today I imported a course into Moodle 3.2 that I exported from Moodle 2.5. The file was about 638 MB.
I had to make the following changes. This is using php56 in Rhel7, so some of the files aren't in the normal locations:
/etc/opt/rh/rh-php56/php.ini
post_max_size = 1G
upload_max_fileszie = 1G
max_execution_time = 600
You do need to restart httpd, which in may case is
# systemctl restart httpd24-httpd
If you forget the restart, the settings won't be applied.
I also needed to update mariadb. In the /etc/my.cnf.d/mysqld, I added this line:
max_allowed_packet = 100M
Save that and then restart mariadb. It should would just as well for MySQL.
Post back if you are still having issues.