1st one:
First of all, open a Trash forum and note its ID.
Then, run this query though your AdminCP -> Maintenance -> Execute SQL Query and paste this query and run.
Code:
UPDATE thread SET forumid='trashforumid' WHERE visible='2'
Do not forget to change 'trashforumid' and if you have prefix use the query as:
Code:
UPDATE prefix_thread SET forumid='trashforumid' WHERE visible='2'
All soft deleted threads will be moved there. And there is a product of me to move threads when closing or deleting to a trash forum. Click here to download it.
Do not forget to change the trash forumid if you install this product through vBulletin Options -> SM Auto Move Threads.