Two 30 amp outlets connected via the Y adapter are well described above. But I have not stayed at any RV park that has had two 30 amp outlets specifically for one site. Maybe two 30 amp outlets on one pedestal to be shared between the two adjacent sites, in which case you could use both if no one was next to you. Don't expect that to be a common option.
More commonly the park pedestal will have a 30 amp outlet and a 20 amp outlet. The Y could use the 30 amp outlet and the 20 amp outlet (with a 30/20 adapter) to get a combined 50 amps, IF, and only IF, the 20 amp outlet is a non GFCI outlet. But codes now require the 20 amp outlet to be GFCI. So you are not likely to find a non GFCI 20 amp outlet except in an older park that has not upgraded.