Thank you for your correction!

1. He needs two canned foods.
1-1. He needs two kinds of canned food.
(Are they wrong sentences?)

2. He needs a canned coke to drink.

3. Shall we have some pizza at a MacDonald's.

(Check the sentences, plese.)

4. Shall we ride a bicycle in/on/at the park? (Which preposition do I have to use? Are all OK?)

5. An old couple found two seats in/on the train. (Are both prepositions OK?)

6. A: Did you see my bag? It was here on this seat. B: Your bag? I heard a ticking sound/noise from the bag. I was so scared, so I threw it out the window. A bomb must have been in the bag.
A: A bomb? Oh,no! It was my clock!

(Is the short dialogue grammatical?)

2 answers

1 is incorrect; 1-1 is perfect.

2 is fine.

3 is OK except for the end -- "...McDonald's?"

4 should be "in the park."

5 should be "on the train." (Don't ask me why!! It's just idiomatic!)

6 is wonderful!! (You can use either "sound" or "noise"; either one works.)
If you are doing a conversation, as you seem to be doing in 6, you might what to put the sentences in quotes. (Essentially, you are quoting what is being said.)

Also a new paragraph is used to indicate changes in ideas, times, places or speakers.

"Did you see my bag? It was here on this seat."

"Your bag? I heard a ticking noise from the bag. I was so scared, so I threw it out the window. A bomb must have been in the bag."

"A bomb? Oh,no! It was my clock!"

I hope this helps a little more. thanks for asking.