Just because of the cost (in time) of loading forms on a mobile, you probably do not want to make a separate form for the file transfer. If there is a user interface component on the file transfer part, the easiest thing to do would be to put all the components into a panel, then move the panel out of view during form loading, and move it back into view when you need it. This is far faster than switching between forms.

Will the file transfer code from a desktop work on a mobile: Maybe. Kind of depends on how you do the communication. A server generally is set to listen for connection requests, which you can't do on a mobile, which means the mobile has to be the client. Simple sockets using TCPClient would work, and would be easy to implement, but that may be how the file transfer is set up now.

One thing that I find unclear in your post is what you want to end up with in the end. What is the program supposed to do? You seem to be trying to merge some functionality between two different apps, but it isn't clear what the final answer would be.