How do you convert a windows movie maker to Imovie?

You need to convert it to QT or mp4 format to use in iMovie. Download and install a free video converter onto your computer. Use the program to convert the (Finished/Published) Movie Maker file.

You may try the Tune4Mac Video Converter Free Version for Mac.

ADDED: You do not need to download a conversion tool, although it can obviously be done. If you would like to know, there is a handful of free online video converters, if you would not like to download one.