Convert String (yyyy-mm-dd) to Date field

[tquinn-16436437]

I have a field in my database that is a string field but it contains dates in the following format: “yyyy-mm-dd” - I need to convert this string into a date dimension so that I can use it in calculations. All of my attempts are not working. My field is called subscription_valid_from. I have included the errors I received in big query. 

Attempt 1: 

parse_date("%Y%m%d", subscription_valid_from)

error: Failed to parse input string "2021-10-08"

Attempt 2: 

cast(subscription_valid_from as date)

error: Invalid date: '05/06/2021'

Can anyone please help?