ok.. i am NOT clearly understanding your intention
you can NOT tun a 30 amp cord into a 50 amp cord
a 50 amp cord has 4 wires that are a larger gauge wire
and the 30 amp only has 3 wires, all your doing is creating a long 30amp dogbone adapter
if you need a longer 50 amp extension you will have too buy one
if you want to use the 30amp ext to plug the 50amp rv into a 30 amp socket
just use the 30 male to 50 female dogbone
and put it between the 30amp cord and the new 50 amp RV cord
like you are now
the 30 amp dog bone takes (1) hot leg and connects it to the (2) in your 50 amp cord
but you Can NOT take (2) 50amp legs and connect them to (1) 30 amp rated wire in your 30amp cord with a 50amp male on the end of a (3) wire 30amp cord
if your not lucky, you could end up with a 100 amp dead short when you tried to plug that in
its against code and extremely dangerous
