All my passwords are gone

What's wrong with them? Can you specify your problem in detail? Or you can try these simple solutions.

1. Check your iPhone and Safari Settings to see whether they are correct. Go to the Settings > Passwords & Accounts > Autofill Passwords, and check if this button is toggled ON. Next, go back to the Settings > Safari > Autofill, then enable the Use Contact Info option.
2. Enable iCloud Keychain. Go to the Settings > [your name] > iCloud > Keychain, toggle the switch next to iCloud Keychain to set it to On. Next, back to the iCloud page, toggle the Safari app from the list of apps.
3. Force Resync Keychain. Go to the Settings > [your name] > iCloud > Safari, disable it, and choose to Keep on My iPhone. After a while, toggle the Safari option again. Next, toggle the Keychain option to disable it and choose to Keep on My iPhone. Finally, toggle the Keychain option again after a few seconds to enable it.