Presumably these are all personally owned devices - and that you have two AppleID accounts. An AppleID account is usually identified by the email address with which the AppleID account is associated.
You can only synchronise devices that are signed-in to iCloud with the same AppleID.
Assuming that the business devices are not centrally managed by an Enterprise/Business - and you wish to change and use your personal AppleID account with these devices, you must first ensure that you have removed the Activation Lock that will otherwise cause difficulties in the future. You can remove the Activation Lock, in each device, by disabling the Find My service from iPad/iPhone settings before trying to use a different AppleID account:
Settings > [Your Name / AppleID] > Find My > Find My iPad - set to OFF
Having removed the Activation lock, you can now sign-out from your business AppleID on those devices that you intend to change:
Settings > [Your Name / AppleID] > Sign Out
Presumably you’ll want to keep any iCloud data that is locally stored on your iPad. If so, accept the opportunity to keep a local copy of your data (e.g., Calendar, Contacts, Notes, Keychain Passwords etc.) - as otherwise this data will be wiped from your iPad as you sign-out from iCloud. If you do not wish to merge this data with your personal data, decline saving a local copy. Be careful with this decision - as once subsequently merged, the process cannot be reversed.
Also ensure that you have signed-out from Messages and FaceTime:
- Settings > Messages > Send and Receive > [AppleID] - scroll to the bottom where you will find your signed-in AppleID highlighted in blue text; tap and select Sign Out
- Settings > FaceTime > [AppleID] - again, scroll down the page to find your signed-in AppleID highlighted in blue text; tap and select Sign Out
After signing out, a restart of your iPad/iPhone is recommended:
Restart your iPad - Apple Support
Force restart iPhone - Apple Support
After restarting, you can sign-in to your new AppleID account from iPad settings - and also sign-in to Messages and FaceTime if necessary. Any iCloud data that you saved to your device during the previous sign-out will be merged with your new AppleID account.
Be aware that device Passcodes are not synchronised between devices. If you wish to use the same Passcode on all devices, they must be manually set to be the same.