To copy value from a column in table a to a column in table b, the syntax is straight forward:
insert into new_table (new_column) select old_column from old_table
But when new_column is varchar and old_column is integer, you will get an error.
You need to use cast function. Update the above query as follows:
insert into new_table (new_column) select cast(old_column as char) from old_table