Be careful of a hardware store and do not ask the home depot guy, they may very well be friendly, but the usually do not know ----.
I say this because manifold bolts are a specific length and if you are a novice. I suggest you just buy a chrome or stainless bolt kit made for the appropriate application.
Also be very mindful of the elbo installation procedure. The are very exact as to using there gasket set and watch the torque spec. .. In other words, RTP "read the poop",