I believe you have to perform an interim step to 3.8.1P to go from 3.5.5; 3.5.5 –> 3.8.1P –> 5.4. I would run this inquiry through Support to validate. But, I believe you need to go to 3.8.1P first just to get configurations files into the proper structure, as the conversion scripts to 5.4 are based on 3.8.1P or >.