Is your rv 30 or 50 amps two ways to tell.
1: Master 120 volt breaker box. Look for the MAIN breaker. the answer is printed on it, also if they are 50's there should be two ganged together 30 will have only one MAIN
2: Look at the shore plug 30 amp is 3 wire (Two flat and a round safety ground)
Round pin may be D or U shaped
50 amnp has 4 wires (3 flats and a safety ground as above)
It's that easy to tell
NOTE: THis is the 120 volt side of life. Now some have asked "How can I have a 55 amp converter on a 30 amp RV
The answer is 30 apples and 55 oranges the 55 amnps is on the 12 volt side. Within limits the two have very little to do with other