Email Contacts

I have a Yahoo email account and an iCloud email account. The iCloud email account does not have all the contacts that are in the Yahoo email account. I want to move Yahoo contacts into the iCloud account and delete Yahoo email account.

I can add the Yahoo addresses one by one into the iCloud account, but they are described as "linked", so I do not know that if I delete the Yahoo account those addresses will be retained in the iCloud account.

Anybody done this?