How to recreate Tableau conditional functions in Powerbi? (See example)

Hello,

I am new in Powerbi and I would like to create the following Tableau function  in Powerbi.

If [account]="A"

or [account]="B"

or [account]="C"

then [A/B/C Goal/Event Ratio]

ELSEIF [account]="D"

then[D Goal/Event Ratio]

ELSEIF [account]= "E"

Then [E Goal/Event Ratio ]

END

I know that there is an option for conditional column. However, in my case I am using a table created inside Powerbi by unioning different queries.

Please someone can help me with this?

Thank you