My baby 120 days old and his weight is 4.86kg and height is 61cm. Please confirm he is healthy. He should put on weight, for that what should I do.

Please use this chart to determine the ideal weight and height for your baby Height And Weight Chart: An Easy Tool to Monitor Your Child’s Health

For boy baby 120 days old 4.86 is less, did you speak with his paed? What was his birth weight? By 6 months the baby will double the birth weight. It's better you discuss with your doctor.