As we said via email, you've never synced with your Zotero account, so you won't find your data online. You'll need to find your local data, which would in the Zotero app on the computer where you last used it. Failing that, you'd have to restore from a backup of your Zotero data directory:
Upgrade Storage
https://www.zotero.org/support/zotero_data#locating_missing_zotero_data
https://www.zotero.org/support/zotero_data#restoring_your_zotero_data_from_a_backup1