How to find formula of compounds ending with ic,ous,ortho,ate,ite etc(For example Ferrous,ferric,sulphite,sulphateetc,.)?

Generally the suffix ate,ite,ide are added with anions and "ous" "ic" are added with cations.
For anions the lowest oxidation state is suffixed with "ide", the next one being "ite" and the highest oxidation states possible is named as "ate".
For example
NaS is sodium sulphide
Na2SO3 is sodium sulphite
Na2SO4 is sodium sulphate
Similarly
Ca3N2 is calcium nitride
Ca(No2)2 is calcium nitrite
Ca(NO3)2 is calcium nitrate
Similarly the suffix 'ous" is added with lowest oxidation state of cation and "ic" is added with highest oxidation state of cation.
So FeSO4 is ferrous sulphate (oxidation state is +2)
Fe2(SO4)3 is Ferric sulphate (Oxidation state is +3)
The use of ortho, pyro or meta don't have any specific rules and they are conventional names used in inorganic acids.