There are various resources available online to get zip codes specific to your country, state, city. I'm including some of those here for reference.
USA:
https://www.centralstationmarketing.com/website-development/tools/zip-code-manager.html
India:
https://data.gov.in/catalog/all-india-pincode-directory
https://www.nativeplanet.com/india-pin-codes/
App does require you to put those zip codes in comma separated format so you can use tools like below to convert your column data into comma separated values.
Free comma separating tool: https://delim.co