Contacts disappeared on iPhone

That only works if you were already syncing contacts with iCloud in the first place. If you were, try logging into iCloud.com using a web browser on an iPad or a computer, click or tap on Account Settings. Then look in the lower left corner to see a link to restore contacts.

Note that you cannot do this on an iPhone and it will only work if you were syncing contacts with iCloud.

Nobody here knows what those suggestions are, so it would be helpful if you stated what it was that you tried.

Were you syncing contacts with iCloud?

Were you syncing contacts from an email account rather than iCloud?

Restore them from the backup you made of them.