Sorry but you can not setup the internet initially without real remote. They do not make replacement remotes for the 3500 stick. And it's too old anyways. If they did make a remote for it it would cost $20, you can buy brand new roku for $30 which will come with a new remote. The 3500 will not receive newer channels going for forward.
Edmund
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.