How do I sync my iPad with my iPhone

i want evreything that is on one device to appear on the other.

You can restore a backup from one device to another to get all data that exists on one copied to the other. This will wipe any data in the restored device and replace it with all the data form the backup however: link-> Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Or if using iCloud to store content and data, you can sign in with the same Apple ID on both devices and turn on the relevant item switches in Settings->Account (top of Settings)->iCloud. Link-> Change your iCloud settings - Apple Support

For other things like Messages, Calls, Clipboard etc…, see here: link-> Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch - Apple Support

For what purpose exactly?

Syncing can mean many things, what is it you are trying to accomplish?