Hello Karimeletre,
We understand that pictures are missing, and we want to help however we can.
You mentioned that the issue occurred after signing into your Apple ID account on your iPad; just to confirm, was the device signed into another account previously?
"For your photos and videos to stay up to date on all your devices, make sure that you sign in to iCloud with the same Apple ID on every device.
You can check which Apple ID your device is using in Settings or System Preferences. You'll see your name and email address. Your email address is your Apple ID."
If photos are missing, the following page has some steps and information that may be helpful: If you're missing photos or videos in the Photos app
You can also find more about viewing iCloud Photos here: Access and view iCloud Photos on your iPhone, iPad, or iPod touch
Thanks!