How to I back up to a previous date?

You mean Restore, not backup.

When you restore from iCloud you choose from a number of available backups.

Remember you will lose everything else since that date, you cannot just recover messages.

https://support.apple.com/en-us/HT204184#icloud

You might find this to be of interest.

Restoring of a DELETED iCloud backup of an iPad

A couple of years ago, Joe_7399 confirmed that iCloud stores your last two backups and each time that you backup, the older one is removed and the new one replaces the one that was the most recent backup. So if you backup every day, today’s backup replaces yesterday’s backup and yesterday’s backup replaces the one from the day before.

Dontbothermepark wrote:

How do I back my phone up to a previous date to collect messages that were mistakenly deleted?

Unless that previous date is one of the backups that are available for you to choose, you can’t find a specific previous date. iCloud saves your two most recent backups. If you backup every day and it’s been three days or more since you deleted those messages, that backup is gone.

If you are syncing messages with iCloud, you cannot recover texts that you deleted.

I am trying to edit my post from above but for some reason, I can’t do so. This is the text that I am trying to add.

I’ve never seen anything official from Apple that states that iCloud stores more than two backups for each device, but I have read in a couple of kb articles where Apple states that you may have multiple backups from which to choose when you restore a backup but they don’t specifically state that “multiple backups” would all be from the same device. I have three iOS devices so I should have 6 backups from which I can choose. Two each from my iPads and two from my iPhone.

Thanks Demo I thought it was more than two!