You might want to make a new query based on the same table for this, because
if you add it as a field in an existing query with other field displaying,
it won't count ALL the records.
In your new query, when you have all the tables in and joined as you need
them, select View/Totals and pull down the ID or some other field into the
grid. In the "Total" row, it probably says "Group by". Change it to say
"Count". Run the query ... see if that's what you're looking for.