iCloud storage

I keep getting emails that say my iCloud storage is full and need to add more. Theses emails are coming from all kinds of crazy user names. They say I can get 50 GB free but need to put in a credit card number that will have nothing charged to it, just to verify my Apple account. The emails contain the iCloud symbol but I don’t trust I emails based on the user names they are coming from. How do I verify if I truly need more storage and these are legitimate emails and not some scam trying to get a credit card number? Please help. It says I’m going to lose photos and other info. I don’t want that to happen.