Currently Smartsheet does not have the option to shows the no. of weeks. Please add this feature in the project schedule. Thanks.
Ran into a scenario for this today where some of the durations on tasks are longer, so the number of days wasn't really helpful, where the team members wanted to see it in weeks. We added a new column (Duration Weeks), where we took the NETWORKDAYS function of the Start and End dates and divided that by 5.