I lost all my contacts

Have you recently deleted or lost connection to an email account? Contacts are associated with email accounts, and the email server is the master copy of contacts.

If they were specifically iCloud contacts here is a help article→Use iCloud.com to restore and recover iCloud information - Apple Support

If they were Google contacts→https://support.google.com/contacts/answer/2753077?hl=en&co=GENIE.Platform%3DiOS

If they were from any other contact source→Manage and delete contacts on your iPhone, iPad, or iPod touch - Apple Support

Well, the contacts were associated with the old email, so if you no longer have access to it there is no way to recover those contacts.