How many movies starring Morgan Freeman are suggested by parental guidance?
'suggested by parental guidance' refers to mpaa_rating = 'PG'
SELECT COUNT(*) FROM movie AS T1 INNER JOIN characters AS T2 ON T1.MovieID = T2.MovieID INNER JOIN actor AS T3 ON T3.ActorID = T2.ActorID WHERE T3.Name = 'Morgan Freeman' AND T1.`MPAA Rating` = 'PG'