Hi, should i stick to giving my 13 month old boy formula or switch to cow's milk already? understand we should be giving our LOs full cream milk now but formula's skimmed milk right?

I understand that baby after 12 month old get nutrients from their solid foods. And drinking milk is only for their calcium intake. However I wasn't sure that the daily food nutrients I prepare is it enough for my 15 month old. Thus for me I still stick to friso 3. As it help in their brain development / or as a nutrients backup and it still maintain his 90% growth. So far so good I won't make any changes like changing to fresh milk. :)