Motorola Migrate is not supported on the G5
If you search for ‘migrate’ in the Community here, you’ll get lots of different answers to this question. Basically, you can use the Google cloud or transfer by copying from your G3 to a computer and back to the G5 from the computer. You’ll need to pay special attention to any Text (SMS) messages you want to keep.
See this post for better information.
In addition to the excellent answer by @jimk I just want to add that your pictures will be at the link below if you configured the Photos app on the old phone to automatically move them to the Google cloud. Even if you didn’t do this it is not too late since the old phone will still work as a tablet and this feature of the Photos app will still work on it: