There's likely to be a story behind your posting, please elaborate.
Given the default app repository is Google's Play Store service, and that the of number and scope of apps in the Play Store is quite massive compared to the much lessor Amazon Appstore service, there must be some reason(s) as to why you're making such a query.
Don't trust Google? That's a common justifiable topic these days. Using Amazon's Appstore is an alternative, but don't ignore that it is tied to another corporate interest, that for whatever reasons doesn't get the same amount of scorn for its also very extensive data mining on its users.
There are a number of dependable, well established, and verified sources to obtain app APKs if you're adept at side-loading them. APKMirror.com is one. F-Droid.org is a very popular repository that focuses on just Open Source apps.