How do I transfer photographs from my iPhone SE to my iPad Pro?

If they have the same Apple ID on each device go to Settings/[your name]/iCloud and turn on Photos.

Open Settings and tap on your name at the top. It will display your name and Apple ID.

In general, 2 or more devices used by one person should have the same Apple ID to share content and settings. However, devices used by different people should have different Apple IDs; the Apple ID represents the person, not the device.