Moving from Google (Android) to iPhone
To start, congratulations on the upgrade :)

Now, what I would do is connect the old phone to my computer (Mac or PC), open Finder (or My Computer), and double-click on the GUI representation of the phone to see the contents, now take the folder marked "DCIM" and copy to your computer.

If you have a Mac, open Photos (10.10.3 or later, for earlier see the Windows method below as it's about the same). Now, import the folder into your photo library and sync the library to your iPhone.

On Windows, you'll need to download iTunes from Apple (nowhere else) and then follow this Apple support article, scroll down to "Sync your photos manually with iTunes."