There are a couple ways to list all the tmux key bindings. If you are not currently in a tmux session, you can still access the list from the terminal with
$ tmux list-keys
If you are currently in a tmux session, then you can take advantage of the tmux environment by either using
<prefix>:list-keys
or
<prefix>?
Any of these will bring up a list of all key bindings available to you within a tmux session on your machine.