I have recently been asked by a friend who has a YaBB 2.1 board to convert it to phpBB 3.0.4 - but everything I’ve found says it can’t be done! And I won’t accept that without some input from you.
His board has 110 members, almost 17,000 posts. We wish to keep the members, topics, forums, and posts. Is there a conversion that can be done?
You’d have to convert the MySQL table structure from one format to the other. I’m sure it’s possible to do, but you’d need to know precisely the structure of each table and create a script with appropriate SQL queries to read the data from one and then convert and write it to the new table. Some data from one table may not exist in the other, so you’ll have to contend with that, too.
ETA: I don’t know where you’ve been looking, but the very first hit on the first Google search I ran came up with this.