Unsupported version of docker-compose.

[levil664]

docker-compose up db

When I ran this command with docker-compose version "3.9", I got:

ERROR: Version in ".\docker-compose.yml" is unsupported. You might be seeing this error because you're using the wrong Compose file version. Either specify a supported version (e.g "2.2" or "3.3") and place your service definitions
under the services key, or omit the version key and place your service definitions at the root of the file to use version 1.
For more on the Compose file format versions, see https://docs.docker.com/compose/compose-file/

I changed the version to "3.3" and everything worked, now dev and main have version "3.9", but everything works for developers.