With all due respect, I really worry about the well-being of someone asking questions about a pretty rugged and potentially dangerous part of the country that indicate they aren't sufficiently aware of local conditions. Having been in some rugged terrain in Brazil myself, I would not underestimate the potential problems, and would definitely seek timely local advice about conditions on arrival, being ready to change plans to a guided trip if it seems more prudent.
I'll quote from Rough Guide:
“..from Cuiaba...as far as Pocone along a paved and fairly smooth 100km stretch of road....The swamp proper begins as you leave the town going south, along the aborted Transpantaneira road...After 145km, having crossed a hundred wooden bridges in various states of dilapidation, the track eventually arrives in Porto Jofre. This is as far as the Transpantaneira route has got -- or ever looks like getting, thanks to technical problems and the sound advice of ecological pressure groups....From Porto Jofre, there are irregular cargo boats to Corumba (2X month).”
What you may see on Google maps as local roads may be best left to the locals with 4x4s who know their way around and are prepared for the exigencies.