Alphard rear wiper fitting problem

[John Sut 1]

Hi all

 

I recently purchased from wish.com a new rear wiper arm set for my Toyota Alphard 2003

 

as there was nothng previously fitted to the rusty bolt for wiper arm I am trying to identify the size of the missing nut that i need to buy in order to fit a rear wiper to the back window

 

Does anyone know what the thread type (is it metric? or inches ) and bolt/nut size is it 3 or 4 mm? 

 

Thanks for any feedback

 

festive regards

john