How can I be sure my Mac has backed up to iCloud?

iCloud isn't a backup service. None of your applications are kept in iCloud and only a small number of programs store data on iCloud and that requires you to save there. The only data stored in iCloud is the data you'd want to sync between your computer and iPhone or iPad such as calendar, contacts, and reminders.

To back up your computer requires the purchase of an external hard drive and use of TimeMachine or other backup program or using an online back service. (An online backup service isn't always a good solution BTW, an external hard drive is preferable and two separate backups on different drives even better.)

LukeTurner2012

Everything on there is extremely important.

If its important, you dont want it there.

Cloud based storage should not be considered for this due to security concerns, and the transient ephemeral nature of cloud storage which can only be quasi-possessed.

Backup and Archive important data across multiple platforms, autonomous external HD, archival DVD and online (not cloud) storage.

The first realization is that your data on your computer is highly vulnerable

The second realization is that you need a HD backup of your OS and data

The third realization is that you need at the very least a secondary HD backup

The fourth and final realization is understanding the fragility of any and all HD & ferromagnetic storage, and that vital data needs to be “frozen” on unassailable redundancies across multiple storage platforms including multiple HD, online backup, archival DVD burns comprising at the very minimum triple platform redundancy of data you have been working on for years or decades that cannot be replaced.

Grab a nice 1TB external HD for $70

https://discussions.apple.com/docs/DOC-6031