Formatting values in two columns from one table to equal the values in one column using SQL VB

Table1
I have Column1 with values like 708-408
I have Column2 with values like 600

Table2
I have Column3 with values 708-408-600

I have a VB script logic that joins Table1 columns that equals Table2 Column3.

CAST([Column1] AS VARCHAR) + replace(str(CAST([Table1].[Column2] AS VARCHAR), 11),'',0) = [Table2].[Column3]

I want to know if the format in the first part CAST([Column1] AS VARCHAR) + replace(str(CAST([Table1].[Column2] AS VARCHAR), 11),'',0)  is the correct format so that it should exactly be in this format ###-###-###.