Hi Angetti,
Thanks for contacting us here in Apple Support Communities. We know how irreplaceable photos can be, so we're glad to help in any way we can.
If the missing photos and videos were removed immediately after signing out of your previous Apple ID, this indicates that the iCloud Photos feature was enabled, and that full resolution versions of your photos and videos weren't downloaded on your iPad. This may be the case if the the option to "Download and Keep Originals" was not enabled in Settings > Photos.
When your Apple ID is signed out of a device with iCloud Photos enabled, any photos not downloaded in their full resolution are automatically removed from your device, as they remain stored in iCloud. If iCloud Photos is not enabled on any other devices with that same Apple ID, those photos and videos will remain in iCloud for up to 30 days.
How long has it been since this previous account was signed out? Are you able to see the missing photos when you sign into the iCloud.com website directly using that older Apple ID on a computer? Here's a guide with the instructions:
Use Photos on iCloud.com on your computer
If so, it's possible to download any photos you'd like to merge to iCloud Photos for your current Apple ID directly from the iCloud.com website, then transfer the photos to iPad. Once those downloaded photos are added to your Photos app on iPad, they'll be uploaded to iCloud Photos for your current Apple ID.
This guide explains how to download photos and videos from iCloud.com:
Upload and download photos using iCloud.com
We're here for you if you've got any questions.
Have a great day!