How to change MS ACCESS QUERY to SQL server 2012

Question

"SELECT b.trn_sno, b.bill_date, b.bill_bno, b.pt_name, b.age, b.sex, iif(d.doct_nm Is Null,'',d.doct_nm), " & _

"b.amount, iif(b.chk_free=1,b.amount,0), iif(b.chk_free=1,0,b.amount), iif(iif(b.app_ref is null,0,b.app_ref)=1,iif(iif(b.rec_ref is null,0,b.rec_ref)=1,'Refunded','Approve for Refund'),'') FROM rec_all as b LEFT JOIN doctors as d ON b.doct_id=d.doct_id WHERE " & txtfld & " and " & _

"b.rw=0 and b.co_code='" & CoCode & "' ORDER BY b.rec_ref, b.bill_date, b.trn_sno"