Assuming you did not use violence when choosing your acquisition parameters, you should have somewhat symmetric lines in your spectrum whose m/z maximum you can pick manually from the data. You can "simulate" the isotopic patterns of potential fragments with an excel sheet and see whether that matches roughly what you see.

Start with smaller, but clearly distinguishable fragments and work your way up to the whole molecule.

Please be aware that MS without NMR support usually is not enough for determining the whole structure.

Thank you for the reply sir but I want information regarding how to write the possible structure of the unknown compound by knowing the mass to charge ratio from mass spectrum please help me to know more information about this

Thanks in Advance

That's exactly what I wrote above: just the mass spectrum may not be sufficient. If you have only the mother ion mass, you can deduct the stoichiometry exactly from the isotopic pattern, but for a structural analysis you will at least need to check the fragments and eventually complement the whole measurement with NMR.