CrocsUnisex Kids Classic K Clog, Black, 6 UK

what size do i need in a big kids croc if I wear a 6.5 shoe

Sizing is very confusing. my daughter wears girls size 13. the sizing chart doesn't mention 13 m, only m13 (men's size 13). is 13 m what i need?

My 9 year old daughter wears a size 4 in regular shoes. I'm wondering if I should size down to a J3 in these?

My 12 year old grandson wears a size 6y in other shoes. what size would he wear? size chart is very confusing.