Hi Lee, there are 2 different trial versions and I'm not sure which one you are referring to - is it the 30-day trial version or is it the "no save" trial version?
For the 30-day trial version you can save your work to a .3dm file and then that file can also be loaded by the full purchased version.
For the "no save" trial version sorry there isn't any way to transfer a model from there into the full version.