0 - 2 of 2 tags for latin to unicode

I want to alter my table column from VARCHAR(4000) Latin to Unicode .
Please help with the alter table syntax if feasible or any differnt approch for the same.

We have some old tables which has Unicode data(Japanese, Chinese, Korean etc..)  but with table defination as Latin for all columns, Which shows in BO report as Junk/ Unreadable character. Now we are trying to add new columns with character set as Unicode using alter statements. The approach we are following is