Delete backups on icloud to create more space

How do I delete backups on iCloud so there is more GB space for future backups. Last time I tried to do this, I permanently deleted my backups by accident resulting in my iphone not being able to back up on iCloud any longer. I do not want to purchase more space. I have 5 GB of storage which is good for me. Most of my space is back ups (3.3 GB). The rest is photos which I have deleted photos and videos I have saved on Google Photos. Please advise. Thank you