How to convert Oracle to SQL Server

I have the following query that I wanted to convert to in SQL Server but not sure how I should go about this. Should I use a CASE statement because I don't see any true/false conditions in this statement. How should I go about this? Thanks!

ORACLE Query: IIF(CD_ID = '999999',TO_CHAR(CL_ID) || TO_CHAR(CD_SEQ_NO) || '999.99',TO_CHAR(CL_ID) || TO_CHAR(CD_SEQ_NO) || TO_CHAR(CD_ID))