I have a 4 months jack russell and he still does pipi and popo inside home

[susette cauve]

Hi, there

my problem is that my dog think that piping and poping inside home is good. We training him to pie on those daipers plastic things when he was a baby, so a month ago we started taking him outside for long walks to teach him to make pipi and popo outside in the street, but when he goes outside he does not do pipi or popo, he will rather make pipi on the training daiper when we come back from his long walk.

What can i do to make him do pipi outside on the street??

Thanks