I just did the same since DNN Forum's won't work properly; on a development box and will be copying over the db and files once it appears everything is good to go.
I was unable to find any update scripts, nor anything like that and ended up having to manually enter all the topics in, one-by-one. We had 191 and it took me a little over 4 or 5 hours to complete.
Below (if it pastes correctly) is the main script I used to get a listing of the current groups, forums, subject, body, etc. from the current forums; 10 at a time.. I then used this for entering each entry in via YAF.
I also had to reset all the user passwords so that I could log into the system as them to add and entry. I have another script which does a group by of the users which have made postings to the current forum so you can see who's made postings and you can change their passwords.
I have other scripts which I can try to post which once done with everything, configure the user ip's, posted dates and times, etc. so that everything matches according to what DNN Forums has.NOTE:
I had to put a space between the single quotes ('😉 and the ending parenthesis because the forum was posting a winky face; as you can see./****** Script for SelectTopNRows command from SSMS ******/
TOP 10 ROW_NUMBER() OVER (ORDER BY Forum_Posts.CreatedDate) AS No,
Forum_Groups.Name as [Group Name],
Forum_Forums.Name AS [Forum Name],
REPLACE(REPLACE(Forum_Threads.IsPinned, '1', 'Yes' ), '0', 'No' ) AS IsPinned,
REPLACE(Forum_Posts.Subject, '&', '&' ) as Subject,
REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(Forum_Posts.Body, '&', '&' ), '%3a', ':' ), '%2f', '/' ), '>', '>' ), '<', '<' ), '"', '"' ), ' ', ' ' ), '’', '''' ), '“', '"' ) AS Body,
Forum_Groups.GroupID as [Group ID],
Forum_Forums.ForumID as [Forum ID]
FROM Forum_Posts INNER JOIN Forum_Threads ON Forum_Posts.ThreadID = Forum_Threads.ThreadID INNER JOIN Forum_Forums ON Forum_Threads.ForumID = Forum_Forums.ForumID INNER JOIN Forum_Groups ON Forum_Forums.GroupID = Forum_Groups.GroupID LEFT OUTER JOIN Users ON Forum_Posts.UserID = Users.UserID
--where Forum_Posts.CreatedDate > '2017-10-25 08:00:00.000' -- Inserted up to this point
ORDER BY Forum_Posts.CreatedDate/****** Script for SelectTopNRows command from SSMS ******/
SELECT Forum_Posts.UserID, Users.Username
FROM Forum_Posts INNER JOIN Users ON Forum_Posts.UserID = Users.UserID
GROUP BY Forum_Posts.UserID, Users.Username