The Intrepid Interior can only be purchased as part of the Pathfinder Voyager + Interior MT which is only available during select ship sales. The pack also includes the Long Range Science Vessel Refit, Long Range Science Vessel Retrofit and Pathfinder Long Range Science Vessel.
Difference in versions
The 2371 version features an Voyager's interior as it was when it was launched. Namely, it features the original Mess Hall with replicators and a normal cargo bay. The 2410 version shows Voyager having received its improvements from the Delta Quadrant. This includes Neelix's kitchen in the Mess Hall, Borg alcoves in the Cargo Bay and Astrometrics.