How Do I Recover Photos Deleted From iPad After Different Associated Device Was Removed?

Before, there was around 3000 photos on my iPad and after doing two things, there was only around 900 photos left. I have three separate devices:

• An iPad
• An old iPhone 6 Plus which I no longer use but contains important photos which were on the iPad before deletion
• My current iPhone

I believe the photos which were deleted from the iPad originally came from my iPhone 6 Plus and resided on my iPad. In addition, I know for a fact that my iPad and old iPhone 6 Plus were connected via photostream as another family member owns the iPhone and their photos appear on my iPad. These devices are all connected under one apple ID, and i'm not sure if either of these following actions I did were the reason for why the photos were deleted:

• 1. I accidently removed my current iPhone from iTunes in the iCloud section. However I don't believe that the deleted photos were on this device. (This could be of limited relevance)
• 2. I removed my old iPhone 6 Plus from https://www.icloud.com/#settings under the My Devices, and since it contained the photos, this may be the reason why the iPad no longer has the photos.

I am fairly certain that the photos deleted from my iPad were from the iPhone 6 Plus, and were possibly shared through iCloud. I'm wondering if there are any possible solutions to restoring my photos based on the info I have given here.

Thank you.