I have 5mg melatonin can I take 5 6 of them I m on 48hrs of no sleep?

Just start with a lower dose. 5-6 tablets of 5mg each sounds a lot.
Effective starting doses for jet lag range from 0.3 to 0.5 mg. Lower doses may work for some people, while others may need a higher dose, up to 3 to 5 mg. However, higher doses may be associated with more side effects such as headache, next day grogginess, or vivid dreams.

Always start with the lowest melatonin dose. According to a Cochrane review, doses over 5 mg appear to be no more effective than lower doses. It is important to note that much higher doses are available for sale in the U.S., but these doses may result in excessively high levels of physiologic melatonin.