Pucallpa is a city in Peru.
It is basically the only direction you can go out of the city by car. Walk to the street Sáenz Peña. This is the main Street going out of the city. Walk to the South West and the road split in two lanes, where the middle one is for cars going further. Walk and waive your thumb, you don't need to go very far to have a good spot. Somebody will stop quickly.
Slow boat to Iquitos
You can take a slow boat going on the Ucayali river to Iquitos. Normally leave on Monday, Wednesday and Friday. 120 Sols (~33$). It takes 4-5 days. Stop at Contamana and Requena.