Pictures from my phone don’t go to my iPad

On your iPhone open Photos. Tap on All Photos. Scroll to the bottom. does it say Syncing with iCloud Paused? If it does, tap on Sync Now. This is just a confirmation of what you posted.

Also, log in to https://icloud.com/photos. Does this include all of the photos on your iPhone? If it does, the problem is with your iPad. Could you be out of space on it?

Pictures will only sync between devices if the devices share an Apple ID and you enable iCloud Photos on both (or all) of the devices.