That will be very difficult and some things will never transfer fully.
Apr. 2018 post by ASC helper Winston Churchill on transferring data from one Apple ID to another. https://discussions.apple.com/message/33333380#message33333380
Look into using Family Sharing to continue to be able to use items purchased with one Apple ID with other Apple IDs. These links will get you started and it is likely somebody else will post a laundry list of Family Sharing documents for you to read:
Family Sharing - https://support.apple.com/HT201060
Set up Family Sharing - https://support.apple.com/HT201088