1. He was shot in his left arm.
2. He shot the bird on the electricity line.
3. He shot shoulders of North Korea during the Korean War.
I think you mean "soldiers" not "shoulders."
4. He is shooting the target on the field.
Almost; he is shooting at the target...
5. The country produces a variety of wheats.
Almost; better to write "The country produces a variety of types of wheat."
6. The company produces steels.
It should be "steel" not "steels."
7. The farm produces barly and chilies.
"barley" and "chili"
8. He produced eggplants and carrots on the farm.
"eggplant and carrots"
9. The company produced three kinds of cars last year.
10. The car was produced in the company.
"by the company" is better
Some nouns do not have plural forms. They imply plural or perhaps plural is all they are. "Wheat" and "steel" are two of these.