From what I've read, it's not possible to only burn fat; the body will lose some muscle inevitably during a calorie deficit. You lose the least muscle when you keep your protein high and work your muscles regularly.
However, 'how many' calories you need to lose cannot be determined by any online calculators, etc. Everyone is unique, and you have to determine your own best calorie level mainly by trial and error. Also keep in mind that the number on the scale does not always reflect actual fat loss. The body seeks equilibrium, and often when a person is losing fat regularly, the body will temporarily fill those empty fat cells with water. The scale may show no loss for several weeks until the body is forced to dump that water--which it does at its own pace, not yours.
You can't rush this process. Focus on your eating and exercise plan, and give it some time.