Inheriting a box of analog media is one of those moments that catches most people off guard. You did not ask to become the family archivist, but suddenly you are. The instinct is to put the box back in the closet and deal with it later, but later often becomes never, and these formats do not age gracefully.
Slides fade and develop color shift over decades. Kodachrome holds up better than most, but Ektachrome and Fujichrome can show significant deterioration. The best move is to convert slides to digital before fading worsens, which preserves whatever quality remains.
Cassettes have their own problems. Magnetic tape sheds oxide over time and can develop sticky shed syndrome, where the binder breaks down and the tape becomes unplayable. Converting cassette to digital captures the audio while the tape is still readable.
Start by inventorying what you have, prioritizing the items that show people no one else has photos or recordings of, and getting a free quote from a local professional. You do not have to do everything at once.