They look like red wigglers to me. Red wigglers will live where ever there is enough organic matter to sustain them. It's not unusual to find them in a garden, at all. The more organic matter in your garden, the higher the numbers of red wigglers there can be.

However, it would be a mistake to purchase pounds of worms and dump them in the garden thinking that they will thrive. There has to be a corresponding and ongoing supply of organic matter to keep them going. Otherwise, they will just die and their only contribution to your garden will be their dead bodies.

On the other hand, if you are just starting out making a worm bin, and you don't have any money to buy worms to start your herd, you can use these worms to get you going. Start a small bin and toss whatever worms you find into it along with your organic output. In time they will multiply, and you will have built your herd from scratch.

Patience is a virtue. The impatient will most likely fail in the worm game. That is one reason why it is suggested to anyone just starting a worm bin for the vermicompost to start with no less than 1 lb = 1000 worms. That will also depend on how big your bin is. It must be relative.