Contacts

Here is a link that you need - Get help using iCloud Contacts, Calendars, or Reminders - Apple Support

Essentially, you have to set your default account on each device to the same account (iPhone/iPad - settings>contacts>default account [set to iCloud]) Once you get all your contacts into iCloud they should be the same for all devices. You will need to go to settings>Apple ID (your name at the top) and select iCloud. Once you do that you will see contacts there. This is where you turn it off and follow the instructions from that link. You can either keep the contacts on the device or erase them. Once you turn contacts back on it should sync the other contacts.