TOSEC is the gold standard for verified ROMs. Look for a torrent or direct download of TOSEC - Atari 2600 (202x). Within the Applications or Games folder, find: Video Olympics (1981) (Atari) [!].a26 — The [!] denotes a verified good dump.

Here are a few options for a post, depending on where you are posting (e.g., a forum, a social media feed, or a blog).

If you download a file named Pong.bin for the 2600, it is almost certainly a homebrew or a misnamed Video Olympics.