Bolt size needed

[chituntang]

I have my S13 Sr swapped to my S14 for about half a year now and found out that my alt belt started to make noise. So I went to the auto store and bought the belt needed. However, I notice no matter how much I adjust the belt, it still make the noise. My guy checked it out and told me I am missing the bottom bolt of the alt. What size and length I needed?

Thanks
Jesse