The person migrating the project will need to use Paratext 8 to migrate it. Paratext 9 does not have the ability to migrate Paratext 7 projects. But once the project is migrated, everyone on the team can work in the project in Paratext 9. There is no need to migrate a project from Paratext 8 to 9, migration is only needed when going from Paratext 7 to 8 or 9.