I am almost exceeding my account's disk quota so I want to clean things up a bit.

I want to back-up all topics that are older than 60 days from one specific forum on the board (it's the chit chat forum where most of the useless spam topics are ) I want to put them back later when we have moved to a new server.

Is there any recommended way to do this? Is there a way to back-up only specific topics?