Merging three instances of RT in another clean instance

im my production environment I had three instances of RT (version 3.4.4)
using mysql as database, and
I need to migrate all objects (Users, Tickets, Historics, Queues, Groups,
Permissions…) of those three
instances in a new instance of RT (same version).
Is there any kind of tool to help this operation?

Tanks in advance,