There is no such thing as "the ZIP code" (singular) for an area code, since area codes are considerably larger than ZIP codes. You will need to look up the ZIP code for a specific address in that area code.
Area code 856 is in southern New Jersey, including Camden and Vineland. ZIP Codes in that area generally begin with 08, but there is no easy correlation of ZIP Codes to area codes.
Los Angeles has several area codes and hundreds of ZIP Codes.
It's not easy, since they are two completely independent systems. Each area code has many different ZIP Codes, and sometimes a ZIP Code may have more than one area code.
There are 300+ Zip Codes in area code 202, which is Washington, D.C.
Area code 308 is western Nebraska. It covers dozens of ZIP Codes.
Insufficient information to answer your question. There are many ZIP Codes in area code 970.
The only "direct hits" are Washington, D.C. (202) and Portland, OR (971). Illinois gets a "close, but not quite" for 618, which has 618xx ZIP Codes around Urbana, IL, just to the north of area code 618. Iowa gets a "CBNQ" for 515: area code 515 = Des Moines, ZIP Code 515 = Council Bluffs. Florida comes close for 321, with ZIP Code 321 for Astor, FL, just north of area code 321. California has several where the ZIP Code prefix and area code are in the same state, but not in the same part of the state. For example, AC 925 = Walnut Creek/ZIP 925 = Riverside. Also, if there were any ZIP Codes beginning with 909, they would be somewhere in southern California, near AC 909. In Wisconsin, area code 534 is Eau Claire and the northern part of the state, while ZIP 534 is Racine. In Missouri, area code 636 is St. Charles, and ZIP Code 636 is Cape Girardeau. Area code 660 in northern MO (excl. KC,MO) is close to Kansas City, KS, suburbs (ZIP 660).
Area code 786 is Miami and the Florida Keys, an overlay on area code 305. It covers dozens of ZIP Codes.
Area code 470 is an overlay on Atlanta's area codes 404, 770, and 678. It covers an enormous chunk of northern Georgia, with hundreds of different ZIP Codes.
There is not a single zip code for Indiana, there are several hundred. You will have to specify a city and street to get a zip code.
Area code 626 serves Pasadena, California, and nearby parts of the Los Angeles metro area. It includes dozens of ZIP Codes.