For automatic transfer, Photostream is easy. Make sure that both the phone and the IPad are connected to ICloud (same account) and signed in with the same APPLE ID.
You do this in SETTINGS. Open settings, then ICloud, then Photostream, make sure that Photostream is in the ON position on both devices.
Once everything is connected, the photo transfer occurs (and continues to occur when you take new pictures). In the Photos section on your IPad, you should open PHOTOS, then MY PHOTOSTREAM and see that the images are there.
You can also use AIRDROP to send a batch of photos. with an IPad 4 or later, and an IPhone 5 or later. Swipe up and open AIRDROP and select the device - the device name should appear in a menu. Or select everyone. Select the photos you want to share with your IPAD, and use the send icon - (it is a square, with an arrow pointing up)
More detailed instructions are here:
How to Transfer Photos from iPhone to iPad with 3 Ways
And, there's always the Apple store, if you can't troubleshoot it yourself.