Greetings for the day. The number of days for the migration is based on the number of files you are using in the version 6.
Its better to discuss through Skype if you are interested.
please contact on my Skype lPlus
I can help you to migrate your FMP 6 solution to FMP 15, I do have extensive experience with FMP for over 25 years and have developed, deployed and maintained many large down through to smaller instances.