Beyond the other answers telling you to remap the prefix key: tmux used to come with an example configuration file that maps to the screen defaults:

    https://github.com/tmux/tmux/commit/2a1bb9#diff-fefa423d67264099ae82d4d2f5422b09

However, it appears that they have removed it at the beginning of the year. At least it's still in the commit history.