Lost Ipad Data

I'd start by logging into iCloud.com and seeing if they either show under Numbers>Browse or in iCloud Drive. Also, did you look in the Files app on your iPad?

You can always restore your iPad from a backup. However, that will overwrite everything currently on your iPad.

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Apple ID (iCloud) username and password, click on the arrow button and see if your data have saved on the iCloud, so that you can recover deleted files on iPad. If you have iTunes backup, you can restore them from iTunes backup. Go to your iPad > Summary > Restore Backup.

That rather depends on what data and how you lost it. More details will help.