Separate iPad from iPhone

Your request is not very clear. Knowing your objective would help us to not to have to guess what it is you need. If you use iCloud with a single Apple Account, the iCloud service does its best to makes sure that the content on both devices remains the same, to various degrees. You can selectively disable the various syncing services to meet your needs. At the other extreme, you can use completely different Apple Accounts on the two devices and then nothing gets shared unless you want to share some things.

Change your iCloud feature settings [iOS and Mac] - Change which apps sync and store data with iCloud - Apple Support -

"When you turn on iCloud for an app, its information is safely stored in iCloud and automatically kept in sync across your devices. When you turn it off, the app will no longer connect with iCloud, so your data will exist only on your device. You can choose which apps on your device you'd like to use iCloud, or turn off iCloud completely."

When you turn off an iCloud feature on a device, information stored only in iCloud for that feature is no longer available on the device. If you turn off Mail, Contacts, Calendars, Notes, Reminders, or iCloud Photos on just one device, you can still view and change your information on iCloud.com and on another device you set up for that feature.