I accidentally deleted the wrong memo on my phone so I was wondering if I could restore it or not and if I can then how?
Try going to your Memo Menu button > Settings > Accounts > Samsung Account, and do a sync.
Hope this helps.
If it has been backed up to Google Drive (which it might have on an S3), try logging into you google account from a browser on a PC and go to https://keep.google.com/#trash and see if it is still there. If it has not been backed up to Google, I am afraid that I don't see any option to recover.