To determine how many pounds of pasta Barry needs to buy for 50 people, we can first calculate how much pasta is needed per person using the original recipe.
The original recipe serves 10 people with 3 pounds of pasta. Therefore, the amount of pasta per person is:
\[ \text{Pasta per person} = \frac{\text{Total pasta}}{\text{Number of people}} = \frac{3 \text{ pounds}}{10 \text{ people}} = 0.3 \text{ pounds per person} \]
Next, we need to find out how much pasta is needed for 50 people by multiplying the pasta per person by the total number of people:
\[ \text{Total pasta for 50 people} = 0.3 \text{ pounds per person} \times 50 \text{ people} = 15 \text{ pounds} \]
Thus, Barry needs to buy 15 pounds of pasta for his family reunion.