I solve it
I had to install a new phpbb in a temp folder
Install this extension
Go to phpmyadmin
Exported table and imported in my original forum
So, with this sql, it can be solved:
CREATE TABLE IF NOT EXISTS `phpbb_thanks` (
`post_id` mediumint(8) unsigned NOT NULL DEFAULT '0',
`poster_id` mediumint(8) unsigned NOT NULL DEFAULT '0',
`user_id` mediumint(8) unsigned NOT NULL DEFAULT '0',
`topic_id` mediumint(8) unsigned NOT NULL DEFAULT '0',
`forum_id` mediumint(8) unsigned NOT NULL DEFAULT '0',
`thanks_time` int(11) unsigned NOT NULL DEFAULT '0',
PRIMARY KEY (`post_id`,`user_id`),
KEY `post_id` (`post_id`),
KEY `topic_id` (`topic_id`),
KEY `forum_id` (`forum_id`),
KEY `user_id` (`user_id`),
KEY `poster_id` (`poster_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin;