dt = dt.AsEnumerable().Where(Function(a) a.Field(of string)("yourcolumnname").ToString.Replace("your old value"," your new value").ToString).CopyToDatatable()
EX :
dt = dt.AsEnumerable().Where(Function(a) a.Field(of string)("ColumnL").ToString.Replace("PC-F50A","").ToString or a.Field(of string)("ColumnL").ToString.Replace("PC-F50A|","").ToString or a.Field(of string)("ColumnL").ToString.Replace("|PC-F50A","").ToString).CopyToDatatable()