Counting days until first value is achieved

Hello,

I've been working on a spreadsheet and am trying to do some variation of a count formula I believe. What I need is to count the number of days it takes for the first value in the data set to come up. Specifically I am tracking mail and want the function to return how many days (each cell in the row is a day) it takes till the first bit of mail becomes tracked. Essentially I just need to find the first value in the row and see how many days it took.

Thanks for the help, it is much appreciated!

Rob