When to plant

Question

What time of the year should I start planting pumpkins, strawberries, and blackberries?

Answer 1

Determining planting time depends first on where you live (USDA hardiness zone to determine last frost date. more info here https://www.gardeningknowhow.com/planting-zones/, and then how you're growing (ground, raised bed, container, etc) These articles tell you about each of the plants you named.
https://www.gardeningknowhow.com/edible/vegetables/pumpkin/pumpkin-growing.htm
https://www.gardeningknowhow.com/edible/fruits/strawberry/growing-strawberry-plants.htm
https://www.gardeningknowhow.com/edible/fruits/blackberries/growing-blackberry-bushes.htm