I wanna recover deleted messages from an iPad

Assuming you don’t house your messages in iCloud, they are saved on your iPad backup. Restore the backup to retrieve the messages that were present when the backup was created.

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

Well, there are many possible reasons. You haven’t told us what happens when you try.

Perhaps you never created an iCloud backup. Perhaps you never created any backup. ...

Oh, using someone else’s iPad or iPhone is always highly risky.

Yes, without the password, you’re stuck.

Your friend can do the restore once (s)he has the iPad returned.