I have about 6000 entries that I need zip codes for.
Is there a good reverse address website, or service I can use to get this?
If anyone here also can do it let me know and I'll chat with you.

Thanks

might be able to use this form:
https://tools.usps.com/go/ZipLookupAction!input.action
heh take a while to do 6000, no idea how often you can hit that form without getting a ban

You probably want to use their existing APIs.

https://www.usps.com/business/web-tools-apis/welcome.htm