Back phone number I deleted

If they are held in your iCloud account then

https://support.apple.com/en-gb/guide/icloud/mme6182cfc37/icloud

If they are held by Google, yahoo!, hotmail etc accounts then contact their support.

If you have deleted one or more contacts, then you can restore them again inside the iCloud website.

From a PC or Mac, go to: https://www.icloud.com

Go to Account Settings. Scroll down a bit. In the Advanced section, you will find "Restore Contacts"