What size bolts are needed to replace Satellite dish swivel bolts?

Hi, Myself and a neighbour recently attempted a DIY install of a satellite dish for use with Freesat. The dish was taken down from a previous dwelling and the angle of the dish was wrong. In attempting to change the angle of the dish the bolts snapped due to rusting. We tried to use replacement bolts but the dish is not stable and moves in the wind! lol. We want to try to get the right bolts on ebay if possible but need to know the type and size of the bolts required so that it is secure. These are the bolts for the swivel arm and not the bolts that hold it to the wall. Any help would be greatly appreciated. Many Thanks.