Welcome to the forum Natasha. At that small, you will need small fruit flies (you can get cultures of flightless fruit flies at pet shops) or tiny crickets/pinhead crickets. You may also be able to collect bugs using a fine mesh net in tall grass (called sweeping). However, if you are inexperienced at this, it might be more humane to let them go where you found them.
To find out the species, please post a photo to this thread and we will do our best to identify the species for you.