Hello FrostAlon,
We see you are asking about files you were trying to back up to iCloud, but didn't have enough storage at the time. We have some questions to clarify the exact issue you need help with.
Are you unable to do a whole backup of your iPhone on iCloud?
Or are you trying to sync specific files to iCloud from your iPhone?
Are you looking for previously backed up or synced files in iCloud?
Let's make sure you have the correct settings enabled for backing up to iCloud: How to back up your iPhone or iPad with iCloud
You may also be able to recover some deleted files through the iCloud website: Recover deleted files on iCloud.com
We look forward to hearing back from you and working on this together.
Best regards.