bbPress.org

I am having trouble importing from SimplePress to bbpress. I’m not sure what the table prefix is supposed to be. I tried wp_ and that didn’t import anything. I tried wp_sf (I think that is the beginning of tables for SimplePress but get this error

Repair any missing information: Continue
WordPress database error: [Specified key was too long; max key length is 1000 bytes]
CREATE TABLE wpzu_bbp_converter_translator ( meta_id mediumint(8) unsigned not null auto_increment, value_type varchar(25) null, value_id bigint(20) unsigned not null default ‘0’, meta_key varchar(255) null, meta_value varchar(255) null, PRIMARY KEY (meta_id), KEY value_id (value_id), KEY meta_join (meta_key(191), meta_value(191)) ) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci;

Is there anything I can do to get this import done?