Macbook Air comes with a install disc which contains a new version of "Migration Assistant" which you should install on the PowerBook. After doing so, you'll see the options you require.
That being said...
I did all of the above and have yet to get Migration to actually occur. (Migration Assistant on the PowerBook gets to the "looking for other computers" prompt, but never finds the Macbook Air -- and three minutes later, the MBA "times out.")
Have spent 2 1/2 hours with Apple Techs (1st and 2nd level) -- but so far to no luck. Hopefully, you'll fare better.