they want to know what they can to help up 为什么不对

they want to know what they can do to help 假如你是想说：他们想知道他们可以帮得上什么忙.
can 后面不能加to,其次,help up 是指帮忙扶起来的意思,
She offered to help him up from the chair.她帮他从椅子里起来
she helped up her grandmother who was stuck in the chair.祖母在椅子里卡住了,她帮她祖母站起来