Create a new column with selected variables of another column

[acg]

I have a column that has different phone numbers plus the names of known  contacts. 

I want only keep  the names of known  contacts and any phone number starting with the country code 61- the rest should be null. 

I have duplicated a column in the Transform Data Editor. 

How do I customase the column in Custom Column?  That is everything except the names of known  contacts and any phone number starting with the country code 61 should be set NULL. 

I am aware that I can use filter options, but due to the sheer number of phone numbers, I do want a code to automate it.

Does anyone know where to look that up? I am thinking I essentially I need something like  a 'case when ' clause saying 

case when [Number] in ('Peter', Frank') or 

        when (LEFT ([Number] ,2) = '61'  then [Number] else null end as [Number_edited]

But it might be easier to just resolve this in sql - but just curious. 

[amitchandak · Accepted solution]

@acg , A new column like

Number_edited =
Switch( True(),
[Number] in {"Peter", "Frank"} || LEFT ([Number] ,2) = "61" ,[Number]
Blank()
)

A column can not take selected value in slicer or filter of another column