How I can filter a dataTable with Linq to datatable?

You are better of using DataTable.Select method, but if you have to use LINQ then you can try:

DataTable selectedTable = tb.AsEnumerable()
                            .Where(r => r.Field<string>("Modul") == value)
                            .CopyToDataTable();

This would create a new DataTable based on filtered values.

If you use DataTable.Select

string expression = "Modul =" + value;
DataRow[] selectedRows = tb.Select(expression);

You can use condition to check rows exist in addition before casting. System.Linq namespace is required for Any() to work

var rows = values.AsEnumerable().Where
            (row => row.Field<string>("Status") == action);//get the rows where the status is equal to action

if(rows.Any())
{
    DataTable dt = rows.CopyToDataTable<DataRow>();//Copying the rows into the DataTable as DataRow
}