You can get a 3.10 alpha image by updating a 3.9 final image (though we do not guarantee results on anything except an original 3.9 final image!) or by getting an image from http://ftp.squeak.org/3.10/Squeak3.10alpha.7069.zip
For more information on the 3.10 release, see http://wiki.squeak.org/squeak/5919
Ralph Johnson and Edgar J. De Cleene