Greetings ToreadorElder,
Thanks for reaching out to the Apple Support Communities! It sounds like you are having an issue with deleting voice memos form your devices. You mention that the memos are on 2 different iPads. Are the memos syncing through iCloud? The storage that's used is divided into different content categories on your device. Storage being used by Voice Memos would be listed under the "Media" category. If you're viewing your storage in iTunes or Finder, the content of the apps is listed under "Documents & Data."
You can find more information about viewing and managing storage here: How to check the storage on your iPhone, iPad, and iPod touch
You mentioned that you previously deleted some voice memos; are the deleted voice memos still in the Recently Deleted folder? More about how to view the Recently Deleted folder under the "Recover or erase a deleted recording" part of this page: Edit or delete a recording in Voice Memos on iPhone
Keepo us posted on the results and have a wondeful day!