How to call a column dynamically in the WHERE clause in SQL

I'm trying to figure out how to call the column in the table where the column name matches the value of a declared variable. In this example, Tbl_B has columns labeled as DPS_YYYYMM such as 'DPS_201911', 'DPS_201910', 'DPS_201909'.... I need to find a way to call the correct column from Tbl_B for the given YYYYMM that matches the @Var. Can you please help?

DECLARE @Var varchar(50)
SET @Var = '201911'

 SELECT ?????
 From Tbl_B
 WHERE campaign_Id = 1 
 

Use Dynamic sql like below

DECLARE @Var varchar(50), @sql varchar(max)
SET @Var = '201911'
set @Var='DPS_'+ @Var;
set @sql='SELECT '+@Var+'
From Tbl_B
WHERE campaign_Id = 1'
EXEC (@sql)