Import baseline from one file to another

Dear all,

I have the following dilemma:

I have several versions of the same project schedule in different files (schedule_v1.mpp, schedule_v2.mpp, schedule_v3.mpp). . One of the old ones I now want to use as a baseline in my current one. Unfortunately I did not baselined it back then. In my current schedule some of the tasks changed date, duration, some new were added and some were deleted.

Is there any way I can save a baseline on the old file and copy it across to the new one?