My passwords are in keychain on my MacBook Air. Can I access them with my iphone13?

Is your iPhone 13 using the same Apple ID as the MacBook Air? If yes and your Apple ID is using 2FA, then you should be able to save them in iCloud. However, unless you are using these 8 devices yourself, you should not have 8 devices signed into the same Apple ID. Or are you referring to multiple devices in Family Sharing? I am not sure if you can share Keychain in Family Sharing.

You cannot share Keychain between Apple IDs, even if they are part of a family sharing group.

Thank you for that information. I was not aware of that.