Your license key requires an "FTC" license item which would look something like this:
# Component: OSL Legacy Migrator
FEATURE FTC ...............
I just did some digging around and confirmed that this is now bundled/included with the base EV 6.0 product.
Just tell your sales rep that you need an "OSL Legacy Migrator" license key and that it is now part of the product (was a separate charge in EV 5.0)
If you and/or your sales rep are in a bind then you could probably get by with a temp key (which includes the OSL Legacy Migrator license item) but I'd recommend getting a permanent key in case your migration activities go beyond the temp key period.
Hope this helps,
Rick