I have a requirement that is probably best made into a process builder. But I've been given the requirement to make it a formula field. I don't know how to do it. 

The requirement: Contact object has two fields Preferred phone (pick list) with options for "Home", "Work" "Mobile" & "Other". The other fields are those corresponding values. 

The other object is called Referral__c. There is a field for prefered phone number that needs to populate whatever is on the contact. 

I need an IF (or something) statement to check whatever is selected on npe01__PreferredPhone__c THEN pull that phone number from the individual field it's housed in and populate it on my field in the referral object. 

I hope this makes some sort of sense. I've googled around and haven't really seen anything that I can build off off myself and don't really have that much time to get it done before delivery day.  I've never been great at IF statements let alone nested ones. 

Thank you in advance to anyone willing to take a crack at this.