The major difference between prokaryotic cells and eukaryotic cells is that eukaryotic cells contain a nucleus and membrane-bound organelles while prokaryotic cells do not. So while in eukaryotic cells the genetic material (DNA) is found in the nucleus, in prokaryotic cells there is no nucleus to contain the DNA. So the DNA is simply contained in the cytoplasm, or the intracellular fluid (mostly consisting of water) found within the cell membrane that makes up the interior of a cell. So the genetic material is found in no particular region inside of a prokaryotic cell. It is freely contained within the cytoplasm.
Usually prokaryotic cells store their genetic material in the region called the Nucleoid Region.