"You can look for that on the Internet."
Translation:Tu peux chercher ça sur Internet.
It could be "le/la", but the English sentence has "that", which is best translated to "cela/ça".
"y" cannot be used, because you would need it to mean "there" or "à + object" with a verb constructed with "à".
"en" cannot be used either, because you would need a construction with "du/de la" or "des":
- (speaking of the Internet) Tu peux y trouver des informations = you can find information there.
- (speaking of the information) Tu peux en trouver sur Internet = you can find some on the Internet.