What is the correct structure to create a dictionary of days where each day will be accessed by its day's number $($for example, Sunday is day $1,$ Monday is day $2$ and so on$...)?$

$\{1$ ; 'Sunday', $2$ ; 'Monday', $...7$; 'Saturday'$\}$

$\{1$ : 'Sunday', $2$ : 'Monday', $...7$ : 'Saturday' $\}$

$[\text{'}$I$\text{'}$ : 'Sunday', $\text{'}$II$\text{'}$ : 'Monday', $...\text{'}7\text{'}$ : 'Saturday' $]$

$\{1,2,..7$ : 'Sunday', 'Monday',... 'Saturday' $\}$