It looks like you're fetching data from an SQL database and converting the Date column into a Date object in R. You already have part of the code that should work well, but there's a small redundancy in how you are using dbGetQuery. Additionally, the mutate function will be more effective once the data is already returned from the SQL query.
The issue here seems to be that you're trying to convert the date format directly in SQL using the CONVERT function with format 103, which already returns the date in dd/mm/yyyy format as a character. If you're trying to convert the column to a Date object in R, you can leave out the SQL date conversion and handle it in R more efficiently.