Anwer is जना हरिम्
As per visarg Sandhi rule Visarga will be removed if previous sound is आ and after visarg next is any vowel or य, र, ल, व, ह or 3rd ,4th or 5th letter of any 5 consonant groups like क च ट त प.
Here I have given you the brief solution for the example and for detailed study you have to study Panini grammar Laghu Siddhant Kaumudi where this process is explained by implementing various rules.