iCloud storage

See the article https://support.apple.com/en-in/HT204247

Delete backups and turn off iCloud Backup for your device

You can delete old iCloud backups for the device you're currently using, or older devices you may not use anymore. iCloud backups are available for 180 days after you disable or stop using iCloud Backup.

iPhone, iPad, and iPod touch

1. Go to Settings > [your name], then tap iCloud.
2. Tap Manage Storage > Backups. 
3. Tap the name of the device whose backup you'd like to delete. 
4. Tap Delete Backup > Turn Off & Delete.

 When you delete a backup, it also turns off iCloud Backup for your iPhone, iPad, or iPod touch

By the way photos have consumed lot of space as shown in your screen shot ( try to reduce them / delete unwanted photos ) .

My understanding is iCloud contains only one backup per device, so there aren't any "old" backups unless there are backups still on iCloud for devices that are no longer in service. If you delete the current device backup and it's the one taking up the space, it will just need that space again unless backing up to iCloud is turned off completely (which is not a good idea, IMHO).

iCloud: Remove an iOS device backup from iCloud - https://support.apple.com/guide/icloud/remove-a-backup-from-icloud-mm122d3ef202/icloud

Settings>your name>iCloud>Manage Storage>Backups

Select the device that was backed up, scroll to the bottom, and choose "Delete Backup".

Limnos wrote:

My understanding is iCloud contains only one backup per device, so there aren't any "old" backups unless there are backups still on iCloud for devices that are no longer in service. If you delete the current device backup and it's the one taking up the space, it will just need that space again unless backing up to iCloud is turned off completely (which is not a good idea, IMHO).

A bit of clarification Limnos I was of the assumption that iCloud saved that last 3 backups. Is that not the case?

Click on the link to read how to "Downgrade or cancel your iCloud storage plan" on an iOS device, a Mac, or a PC. --> https://support.apple.com/HT207594

Here's another one saying they have only ever seen one backup per device. https://discussions.apple.com/thread/252340189?answerId=254420151022#254420151022