Find.ly does not store search results, so there is no page 2 to fetch later. A search returns the whole list in one response, up to 5,000 items, and you page, sort and filter it on your side at no cost.
There is no page, offset or cursor parameter. In the body, such a field returns 422 invalid_input; in the URL, anything other than format is ignored. Running the same search again to get “the next page” uses another request and returns the same list.
Read the counters
When truncated is true, the items beyond 5,000 are not reachable. Narrow the search instead: for Intelligence Search, lower max_results or set date_from / date_to.
Page on your side
Keep the response if you need it again: another call is another billed search.
Export Phonebook as text
Phonebook can return the list as plain text, one selector per line, with ?format=txt. It is the same search at the same price, not an extra request. See Raw files and text output.