fixed link issues with README.md

README.md

@@ -26,11 +26,11 @@ Run `go run ./backend/main.go`, which will start a backend instance at
 
 Note that if `mind.db` doesn't exist in the working directory, it will
 be created and be initialized by the code in
-[`backend/db/migrations`](backend/db/migrations).
+[`backend/internal/db/migrations`](backend/internal/db/migrations).
 
 ### DB-related
 All db-related operations (e.g. queries) are under
-[`backend/db`](backend/db).
+[`backend/internal/db`](backend/internal/db).
 
 ## Running tests
 To run tests, we provide a simple CLI-based frontend client at