Convert String to Date

Convert String to Date

I need to be able to take my string and convert it to date, however I am no SQL master. I am getting nothing returned because the time is being captured in the date field, 

What I want is only the date (MM/DD/YYY) to be captured in both "Pick_Date" and "InvoiceDate" Columns. Current its capturing (MM/DD/YYY/HH/MM/SS) 

The query I have written is below

Select InvoiceDate, Grade, GradeName, sum(GradeNW)/sum(ProductionNW) * 100 as "percentage" from prod_sum_nw, grade_sum_nw
Where InvoiceDate = Pick_Date
Group by InvoiceDate

Thank you in advanced