One serving would be 3 to 6 ounces (3 for women; 6 for men) and would be roughly the size of your palm.
THE SIZE OF A DECK OF CARDS.
A serving of meat and meat alternatives is approx. 3 oz (85 grams), regardless of gender. A male is recommended to have one to two more servings per day than a female of the same age group (child, adult, senior).