If the doors are about the same size, and you have at least one gas spring that is marked, you could order more of the same.
To calculate the the size needed, there are many complex ways to figure it out, but here's a simple way. If the door has the pivots present, use a bathroom scale and a stick (broomstick, dowel, etc.) cut to length to prop the door open horizontally (parallel with ground) with one end of the stick supporting door at the pivot point on the door and the other on the scale. The scale will read the maximum force needed to hold the door at that point. If you moved the stick out or in from that point, the force would change, so be sure to measure at the pivot point. With that number, the compressed length of the gas spring, (door closed) and the extended length (door open all the way up against RV side) You should have enough information for a shop to sell you the right gas spring. NOTE: Make sure they know the weight is calculated for one. If you are using two gas springs, they will have to adjust properly.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI