How can I find the version of Docker I am using?
For the daemon's version (meaning the engine's version) that's running on your server:
$ dockerd --version
Docker version 20.10.2, build 8891c58

For your client's version that's running on your local computer and with which you send commands to the daemon on the remote server:
$ docker --version
Docker version 19.03.13, build 4484c46d9d