Address book
How to send address from an email I try to my address book? ( don't know where the address book is either -my contact?)
iPhone 11, iOS 14
Hi nan-s-k,
welcome to the Apple Community, where some of us do our best to help each other.
The iPhone address book is called "Contacts"
In the Contacts app 
, you can view and edit your contacts
Apple support has an article online (blue link below) to help use "Contacts"
Add and use contact information on iPhone:
https://support.apple.com/en-au/guide/iphone/iph3e0ca2db/ios
For example:
Share a contact:
Tap a contact, tap Share Contact, then choose a method for sending the contact information.
Sharing the contact sends all of the info from the contact’s card.
Other useful articles:
Edit contacts on iPhone
https://support.apple.com/en-au/guide/iphone/iph89a9c71d8/ios
For phone numbers:
Use Contacts from the Phone app on iPhone:
https://support.apple.com/en-au/guide/iphone/iph9b90d0aba/ios
Hope this helps you do as you wish :)