Exchange 2003 from Exchange 5.5

I am upgrading from Windows NT 4 and Exchange 5.5

I’ve decided to just do everything fresh, no upgrade . But with Exchange 2003 what is the best way to copy mailboxes over to 2003 from 5.5? When I run setup it has options Exchange 5.5.What does that do, will it let me migrate them over?

Can I still migrate or copy mailboxes over to 2003 manuelly?