You can reorganize it like this:
1, use a headphone cable to remove two headphones.
2. Weld two plum blossom plugs on the original two earphone wires respectively.
3. Insert the plum blossom plug into the audio input socket of the stereo, and insert the other end into the earphone and computer earphone jack.
Headphone plug: 1- ground. ? 2, 3 core wire
Torx plug: 1- ground wire. 2- Core wire.
4. When welding (as shown in the figure), the ground wire (1) of the two earphone wires must be the same as that of the plum blossom plug (1).
Note: If the audio speaker has "buzzing" sound during use, you can use shielded cable instead of earphone cable.