I assume that you are talking about what happens in Book XXIV, the last book of this epic. By the time that this book takes place, Achilles has already killed Hector. Priam is, of course, the King of Troy and the father of Hector. He wants to get his son's body back from Achilles.
In Book XXIV, Zeus sends a messenger to Priam to tell him to go to Achilles and ransom Hector's body. He also sends Achilles' mother to tell Achilles that he had better give Hector's body up to Priam.
So Priam goes to Achilles with a very valuable ransom. That is how I would answer this question -- by saying that Priam brings a very valuable ransom to exchange for Hector's body. If you want to list what he brings, here's a quote that will help you:
So saying he lifted the lids of his chests, and took out twelve goodly vestments. He took also twelve cloaks of single fold, twelve rugs, twelve fair mantles, and an equal number of shirts. He weighed out ten talents of gold, and brought moreover two burnished tripods, four cauldrons, and a very beautiful cup which the Thracians had given him when he had gone to them on an embassy; it was very precious, but he grudged not even this, so eager was he to ransom the body of his son.