OK, the problem here is that it's NOT a stand alone cassette deck, essentially it's part of a cheap music system, separated off to give the impression that it's separates. There are essentially two variations on this theme, one has ribbon cables connecting the two items (in fact probably connecting them all), and one has no power supply in it (with power fed from the main unit it's part of) and separate phono/RCA sockets for IN and OUT - presumably it's this type? (otherwise it's useless).
Mostly the power for the cassette is just AC, fed from a winding in the main unit.
A good idea would be to google the make and model, and find a service manual - it will be obvious then what's required.
I would imagine there's also a good chance it doesn't work?, most cassette decks are long since worn out.