Adopting a new software system often involves moving substantial data from one environment to another and quite frequently this needs to be done more than once: first in a test phase, later an initial 'real' move and possibly again if the two systems are to run in parallel for a period.
Depending on requirements this data migration be may involve a level of 'intelligence' with a set of rules applied to 'shape' the data into the new format.
We have migrated a few gig over the years :) and would love to help you move yours.