。
She told the children not to play in the street.
Literal
She [topic-は] children [to-に] street [at-で] play-not [as-ように] cautioned.
~ないように注意する ('to caution / warn [someone] not to do X') combines the negative ~ない with ~ように (the indirect-command marker) and 注意する ('to caution, to be careful, to warn'). The whole pattern is one of the most useful for warnings — '気をつけるように言う,' '~ように注意する.' The location 通りで ('on the street') uses で as the locative of activity. Streets are a common site of play in older Japanese neighborhoods, but with traffic concerns, parents reliably warn children off them.