Mark,

I suspect you're not going to like this advice but get help. A structural
engineer can make a reasonable guess as to the weight that you are lifting
and suggest where to locate temporary supports. Once you know where the temp
supports go you may want to pour some footings. You'll need support columns.
The type with screw jacks are good for this. See if you can rent the
columns, screw, and bottle jacks. Use a level to be sure that your support
columns are plumb. Now at each jacking point you'll have a bottle jack under
a 6x6 under the barn's sill plate. At each end of the 6x6 you'll have a
support column. Jack up, raise the support columns to support the weight,
move to the next jack and repeat.When you're done the barn will be up on the
support columns and you can remove the bottle jacks, pour footing and build
a foundation.

Dave M.