A Type J plug in Guinea-Bissau?
Not directly — pack an adapter.
Guinea-Bissau's Type C sockets don't take a Type J plug. A plug adapter solves the shape problem — it changes pins, not electricity. The wall delivers 220 V at 50 Hz (198–242 V within tolerance) — if your device isn't rated for that (look for "100–240 V" on the brick), an adapter won't save it.
Grid facts verified against IEC World Plugs — Guinea-Bissau. Physical-fit verdicts derive from pin geometry and each socket standard's acceptance list — not safety advice.