All the negatives the original owner took on that film pack are probably still inside it. To open the film pack, in your changing bag slide off the part that shows to the right in your first picture. Then it will pretty well spring apart. Peel each negative from the paper tape to the paper sheets. Now, you need to put them in something to process. Best thing by far is the Nikor sheet film tank, adjusted to the correct size for these negatives. If you don't have then, you can "taco" them in plastic tubes put into a Nikor tank. Barring that, you're going to have to process them in a tray in complete darkness. Try HC-110 Dilution B about 7 minutes.