Hi, My Charlotte is 7 months old and I'm slowl...

Hi, My Charlotte is 7 months old and I'm slowly drying up and also want to supplement. My 10kg baby has now started waking up during the night starving. Do I start with the 'Infant/starter/step 1 formula or the step two/6 month formula?' The lady at the chemist says in the infant one but i'm not convinced. Any brand tips?