Export or merge multiple archived conversations

Apologies if this is documented somewhere… have searched endlessly with no luck (found many similar unresolved threads). I need to export multiple archived conversations (for one user within a date range, if possible). I.e. collect all IM conversations for one user from Jan 2015 - present.

Any help is very appreciated! Openfire 3.9.3, Monitoring Service 1.4.2, MySQL database