Both Der Bürger (the citizen -- one of them) and Die Bürger (the citizens -- many of them) are items in this unit.
Listen carefully to hear what is being said, or watch carefully to see what you are being asked to translate.
Der Burger (the burger, the meat sandwich) is not an item in this unit.
Pay attention to the umlauts -- if you can't make a "ü" then write Buerger rather than Burger as that is a different word.
Yes: like a lot of masculine words that end in -er such as Lehrer "teacher" or Käfer "beetle", Bürger is the same in the singular and the plural.
Mind your spelling, though: Bürger has a capital B (since it's a noun) and then a ü. (If you can't make a ü, write ue instead: Buerger. Burger is a completely different word in German and refers to a meat sandwich.)