RAID is provided by the md driver. mdadm and raidtools are merely userland tools that manage arrays.
So there is no conversion necessary when working with either of these utilities. You should be able to use them interchangeably, assuming there are no unknown bugs that might cause a problem.
One caveat: a lot of popular distributions (RedHat, for example) contain an init script that activates arrays found in /etc/raidtab when the system boots. If you are moving to mdadm and are a previous user of raidtools and /etc/raidtab, you might want to check the files in /etc/init.d and make sure that there are no RAID-related scripts that use raidtools. In many cases simply renaming /etc/raidtab will suffice.
Sorry for the confusion.