Your instructions are completely correct, but it might make more sense to look at the bands of metal rather than the insulator between them.
TRS stands for “Tip, Ring, Sleeve”, referring to the 3 contacts on a TRS jack - one for the left channel, one for right and one for ground. TRRS as you might guess has an extra ring to provide a contact for the microphone as well. So you’re looking for the metal tip, two rings of metal and then the metal sleeve.