The little ッ is a pause (small tsu). I am assuming this is how the Japanese see Americans pronounce Conrad. In Romaji it would be Konraddo. But it is pronounced Conrad-do, with the "-" being a noticeable but not-too-long pause. Most Japanese people will probably spell Conrad - コンラッド because they see it this way (I.E. English speakers pronounce the Spanish name Laura- Loh-ra), but you can spell this name however you want, like コンラド, just know that the "official" spelling is with the little ッ.