Guys my science fair project tells me to use 3 agar petri dishes prepared with blood agar but what i am about to buy tells me that they have hardy diagnostics plate, blood agar, 15x100mm, 10/pk.

it has hardy diagnostics plate not petri dishes so what should i do? and is it the same thing?

I was able to find the page on the company website from which you are ordering - this is a direct quote from the webpage listing the features: "Polystyrene Petri plates feature raised rings for stacking ability and prevents sliding."

so yes, the item you are ordering does in fact use petri dishes. Hardy diagnostics is the company, and they simply use the word plate rather than dish.