Hello Linda,
I would start off by removing the accounts that are missing folders from your iPad then reboot the iPad.
Then check from a web browser the mail settings, and make sure IMAP is turned on.
Then I would re-add the accounts one at a time with a reboot of the iPad after each account is added.
You can tap or click here for further troubleshooting and directions on confirming IMAP is enabled for said accounts.
Let us know how it goes!