It depends on how vigorous the plant is, assuming that you have the vine trained the way that you want it. My grape plants die back after harsh winters so the crowns of the plants are just above ground level and the canes come off the crown in all directions. I thin out the weak ones soon after they start growing. Letting a young plant fruit before it gets established could kill it over the winter.

Where are you located? Grape vines here live for many decades and never die back to the ground! But they do need consistent pruning each late winter or early spring.

A 3 year old vine is not a particularly "young" plant and should be ready to bear now. Your grape was likely already at least a year old when you purchased and planted it maybe even older. The first year in the ground you need to remove flower/fruit to allow proper establishment and the development of the root system. And the second year, it may or may not produce any flowers or fruit anyway. By year three (at least a 4 y.o. vine) you can let it fruit but do not let it produce heavily. Thin out the clusters so that each has 12-18 leaves supporting it or roughly each cluster about 18-24" apart.