Namaste / Hello, Aap kaise ho ? Both the answers are correct. However, for giving respect to father, U may add ' ji ' ok ? Keep it up.

He is my father = वह मेरे पिता है Vaha mērē pitā hai My father = मेरे पिता Mērē pitā

my father- मेरे पिता(mere pita) (मेरे पापा)(informal- mere papa) (here we have used "mere" because we are giving respect to father, when we do that singular changes to plural sentences) he is my father वह मेरे पिता(or पापा) हैं | wah mere pita(or papa) hain we can also say "pita ji" पिता जी to add more respect.