You need to make sure the FTD are on version 6.2.3 then upgrade your FMC from version 6.2.3 to 6.6.x which is the supported direct upgrade.FMC 6.6.x can manage the FTD 6.2.3 but you will need to upgrade the FTD to same version as FMC in this case 6.6...
You can configure Policy Based Routing using FlexConfig on FMC.Check following videos:https://www.youtube.com/watch?v=lakHhw9CR5Yhttps://www.youtube.com/watch?v=MKcSBTJ55e8&t=18s