Answer:
toque or toco
Step-by-step explanation:
The answer depends on what tense you are supposed to be using. If you are using present tense, the conjugation would be toco because the verb is regular in present tense and the regular yo form ends with -o.
If the tense is preterite, it should be toqué, because tocar is irregular in the preterite tense.
If you have never heard of the preterite tense, it is most likely in the present tense which means the answer is toco.