Longan is not a common fruit in America. I take it you are from the Philippines, or are a Filipino or Vietnamese immigrant?

Either that or you are an advanced gardener interested in rare and obscure tropical fruits. Longan is related to Lychee, for any of you readers who did not know.

This may be surprising, but pruning can actually stimulate Longan and Lychee to produce more fruit. Pruning is usually done after the crop has been harvested to get the timing right for the next season's flowers.

Generally if the tree sends out flushes there will not be fruit that year.

Your trees are only 3 feet tall. You do realize that it takes Lychee trees several years before they start producing fruit? Let your tree grow at least another year, and do not be expecting fruit from it this year.

Disclaimer: I am not an expert in this area, so maybe someone else here will have better advice to give you.